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The Absorption of Magnesium from the Alimentary Tract of Sheep
j.
10
COMPo PATH.
1956.
VOL.
66.
THE ABSORPTION OF MAGNESIUM FROM THE ALIMENTARY TRACT OF SHEEP By
J.
STEWART
Moredun Institute, Gilmerton, Edinburgh
and
*E. W.
MOODIE
Royal (Dick) School qf Veterinary Studies, Edinburgh INTRODUCTION
There is still much controversy regarding the cause of seasonal hypomagnesaemia and hypomagnesaemic tetany in both cattle and sheep, and a survey of the literature reveals that little or nothing is known regarding the absorption of magnesium from the alimentary tract of ruminants. The following experiments, therefore, were carried out as a preliminary to the study of the factors influencing magnesium absorption and to ascertain if possible the region of maximum absorption. Sheep were selected as the most useful animals for the operational procedure and manipulation. They were not allowed food for the twelve hours preceding operation and at the end of each experiment were killed whilst still under anaesthesia. OPERATIONAL PROCEDURE
Anaesthesia was induced and maintained by the use of Pentobarbitone Sodium Solution (I gr. per m!.) given intravenously. The experimental animal was placed on a heated operating table and the abdominal cavity was opened by an incision made in the right flank through the skin, abdominal muscles and peritoneum from a point at the edge of the last lumbar transverse process to the region of the xiphoid cartilage. Blood samples were taken from the jugular vein immediately preceding dosing and after completion of the operation to observe the changes in the mineral concentration of the venous blood during the course of the procedure. Prior to, and at intervals during, the operation samples were taken from the carotid artery to represent arterial blood. Blood was also taken from the following veins to represent drainage from the various parts of the alimentary tract-right ruminal to indicate drainage from the rumen, left gastric from the abomasum, gastro-duodenal and anterior pancreatico-duodenal from the duodenum, intestinal from the intestine, caecal branch of the ileo-caecal-colic from the caecum, colic trunk of the ileo-caecal-colic from the colon, and the left colic to represent drainage from the terminal colon. In one series of experiments samples of the contents of the various parts of the alimentary tract were taken at the same time as the blood samples representing drainage from these parts. This was done by means of cannulae inserted at the time of operation. The cannulae used for the rumen and caecum had an external diameter of 3 cm. and an internal *Now of Queensland Veterinary School, Yeerongpilly, Brisbane, Australia.
J.
STEWART AND E. W. MOODIE
I I
diameter of 1.25 cm. while those used for the small intestine and abomasum had an external diameter of 8 mm. and an internal diameter of 5 mm. Both blood and alimentary tract contents were assayed for calcium, inorganic phosphorus and magnesium-calcium by the Kramer-Tisdall oxalate precipitation and permanganate titration method, magnesium by a modification of the Denis method, and phosphorus by the Fiske and Subarrow method. RESULTS
Abs01ption of Magnesium Throughout the Alimentary Tract In the present work it was assumed that, if the concentration of an element in the blood from the vein draining a part of the alimentary tract was significantly higher than that of the succeeding sample from the carotid artery, absorption had taken place from that part. Objection to this assumption might be raised if there was a long interval between the taking of the venous and arterial samples, but in the present work the interval was very brief, being only of a few minutes' duration. The value for venous blood was always compared with the value of the succeeding carotid sample. Great care is necessary in the interpretation of the data and the general trend of values in the contents of both the venous and carotid samples must be examined as well as the values for the contents of the various parts of the alimentary tract under consideration. This method has been adopted by most of the workers in this field of ruminant physiology (Masson and Phillipson, 1951; Parathasara thy, Garton and Phillipson, 1952; Schambye, 1951; Scarisbrick and Ewer, 1951). In order to ascertain whether the anaesthetic would have an effect on the blood minerals under examination two sheep, A and B, were anaesthetised and kept under total anaesthesia for four hours, samples being taken at intervals from the jugular vein. Two sheep, C and D, were kept in the same pen but not anaesthetised and were bled at similar intervals to A and B. It will be seen from Table I that anaesthesia had very little effect on the blood calcium, magnesium and inorganic phosphate, a greater variation being apparent in C and D than in A and B. In the case of sheep I, 2 and 3 the operational procedure was carried out to ascertain if the manipulation of the animals, consequent on the technique employed, would exert a greater effect on the blood minerals than that of total anaesthesia, as shown in A and B. From Table 1 it was seen that the procedure had little effect on either blood calcium or magnesium, although there was a slight variation in the contents of the various veins sampled. The variation in the phosphate content of the veins was greater than that of the calcium-and magnesium, but there was no evidence of any serious alteration due to tissue response after manipulation. Much has been written regarding the diurnal variation of blood phosphate but the data in Table I showed little change over three or four hours.
12
THE ABSORPTION OF MAGNESIUM FROM ALIMENTARY TRACT
From the data of Table I it was also apparent that little could be d educed regarding the site of magnesium absorption. There \vas TABLE
I
EFFECT OF THE ANAESTHETIC AND OF THE OPERATIONAL PROCEDURE ON THE BLOOD MINERALS
I
Anaestlutised
No anaesthetic
C- - --
- - - - ---S-he-ep-A--, Sluep B --Sheep Sheep -n -mg/lOo ml mg/roo ml mg/roo ml mg/roo ml Time - Mg pC;; Mg - p-C;; Mg ' -PC;; Mg -P-iCa
1-
-P-re--1T s ! hr 8'5 8'5 I " 8'5 2 " 8 '5 3 " 8'3 4 "
3'38 3'38 3'35 3'3 1 3 '2 9 2,81
6'54 5'74 5'54 5'90 5'74 5 '54
~ 2'40 10'1 10' 1 10'0 10'2 10'1
------ ----- - Jugular
I
, •
Carotid
I
.'
~
~
p
9,6
1,89
4'04
~~ 9,6 8'5 9'9 8'5 g'l 9'9 8'1
2'09 2 '01 1,87 1,86 2'27 1'75 2'01
1--=-1 -
2 '44 2'44 2 '44 2 '48 2'42 2'12
Is.;- ~ 2 ' 38 9 ' 26 7'56 7'40 7' 26 6'76
10'9 10 ' 9 10'9 11'2 11'2
~
~
~
9'1
2'34 4'50
p
5'26
4'71 7'14 8,85 5'40 5'40 5' 13 7'25
4'97 4 ' 97 4,68 5'60 5'52 4'97 5'88
-
-J-U-gU-I-a-r-2----,-·--+I--I --=-I ~
-;;;-:36 9,80 9'26 9'52 9,80 8'70
Sheep 3 mg/ roo ml serum
- -, - --. ----11-
1-
2'78 2 4' 0 2 '3 6 1 2'271' 2'03
Sheep 2 mg/roo ml serum
5,62 --;.;- 2'24
------------I--~i-
Carotid 2
10'9 10'9 10'9 10'9 10'9
Sheep r mg/lOo ml serum
Blood sample
Rumen Abomasum Duodenum Intestine Caecum Colon Terminal colon
~
6'10 2'41 6 ' 23 2'42 6'4 1 2'40 6'28 2'40 6'30 2'38 6'10
8,8 9'1 9'0 9'1 9'1 9'9 8,8
2'08 2'18 2'17 2'21 2'22 2'29 2'24
-
11'3
'-
-
;- -
~ I
p
--1- 3'03
I 3,88
~~I-;8~ 10'9 11 ' 1 11'1 10'4 10'4 9'7 11'3
---2 ,87 3 '14 3'56 3'29 3'56 3'21 3,80
4 '52 5,60 4'76 4,62 5'19 5' 8 4 6'02
~ 2'22~~~! --=9 ' 11 2 ' 3 0 5'40 1~~i~~
a remarkable constancy in the mineral content of all veins for any one animal and practically all the values were within the normal range for sheep. In order to increase the magnesium content along the whole tract 4 oz. (I 12 g.) of magnesium sulphate were given orally to three sheep, (4, 5 and 6) and two hours later operation was commenced. In the case of 6, samples of the contents of th e various parts of the alimentary tract were taken by cannulae as described above, but owing to the extremely solid nature of the contents of the colon and terminal colon it was not possible to obtain samples from these two regions. The results are shown in Table 2. Slight absorption of magnesium took place from both the rumen and abomasum of both sheep 4 and 6 and from the abomasum of sheep 5. This was true also of the duodenum and small intestine
J.
STEWART AND E. W. MOODIE
except in 6. It was apparent from the assay of the samples of the contents of the various parts of the tract that within the period TABLE
2
ABSORPTION FROM ALIMENTARY CANAL AFTER DOSING WITH 112 g_ MAGNESIUM SULPHATE
Timeo! sampling
I Sample
Pre-dosing Jugular Blood Jugular BIDDd 2 hrs. after dosing CarDtid Blood 2-2! hrs. after dDsing
2! hrs. after 2!-3 hrs. after dDsing
Rumen B1DDd Rumen CDntents Abomasum Blood Abomasum Contents Carotid BloDd Duodenum Blood Duodenum Contents Intestine Blood Intestine Contents
3 hrs_ after Carotid Blood
- -3-4 hrs. after dosing
Caecum Blood Caecum CDntents CDlon Blood Terminal Colon B1Dod
I
Sheep 4
Sheep 5
mg. per cent_
mg _per cmt
Cal
Mg.
P.
~1 2'32
Ca_
Mg.
'- P.
- - - - --
5"60. 10·66 2'39 5.67 10'4 3 -10 4'97 10'26 3.66 5'50.
- - - - - - - - - - -g·86
Jugular BloDd
mg_per cent P. Ca. Mg. -~-
- -- --
4- 17 7'50.
10. '0.
3'27
5"95
9-7
4-0.4
7-50. 10.-0.0. 4'5 1 7'08
g- I g'2
2'78 9'95 3'9D 8·60
g'l
3'9D 8'70.
------
- - - - - - - - - - - -- - - - - 10.-2 4'0.4 6'55 10'13 4· D9 7'0.2 9-3 5"53 9'35 -. - - - 27-0. 145-0. 50.'5_ 10. '0
-
--
-
-
3- 66 6'50. 9'78
- - - -I-
-
-
4' 19 6-88
g'6
5- 20.
7-70. 10 '43 5"4 2
-
9-3
4'93 -
8-05 10-40. 5"5 6 -
-
-
8 -5 5"66
-
7- 1 3
-
10'1
30. -0. 129-0. 35"2-
------
------ -
8 ·8
4 ' 28
8'5
4 ' 39 g-80
11'5
- ----
44- 0 143'0. Ig·6 8 -0. 4-4q 9'35 44 -0. 15 1'0. 17'7
- - - - - - - - - -- - - - - - -g-g 4'0.6 4.86 10.'10. 5'10 6·88
7'70.
9'73
7'9
4 -30. 10-45 10'26 5"5 6 6'9 2
7-9
- -- - - - - - -----8 -3 5"3 6 9'48 9'9 4-97 10'45 9'73 6-06 7'02 - - 93-0. 277-0 g' l
g-6D 5'4 2 6·84 4'97 - - --- - - - - - - - - - - - - - - - - 4 hrs. after Carotid BIDod
Sheep 6
g'2
10.' 1 8 -33 11 '20. g·86 6'4 1 8'40.
1~17.66~i~
5" 25
8-0. 5"22
9'24
-
-----8-3
5"22
8·0.
5"49 9'95
9-35
---------6-0.6 8'47 1
of the experiment, four hours, the dose of magnesium sulphate had passed to the caecum, but there was no real evidence of absorption from the caecum and colon of magnesium or of calcium and phosphate. As regards interaction of magnesium with calcium and phosphorus a point of interest is that whereas there was a slight fall in the calcium content of the venous and arterial blood there was a considerable rise in the inorganic phosphate contents, except in 6 which had a high phosphate content before the dose was given. In order to -see the effect of the magnesium ion the experiment was repeated using magnesium nitrate instead of sulphate, and so sheep 7 and 8 were given I 12 g. magnesium nitrate two and a half hours previous to the operational procedure. To ascertain the
14
ABSORPTION OF MAGNESIUM FROM THE ALIMENTARY TRACT
interaction of increased phosphorus and increased calcium intake on the magnesium content of the blood sheep 9 and 10 were given 112 g. sodium dihydrogen phosphate (NaH 2P0 4 .2H 20) and sheep I I was given 112 g. calcium chloride (CaCI 2 .6H 20). The analytical results are shown in Table 3. The most striking result from the dosage of magnesium nitrate was the much enhanced absorption of magnesium, as the blood magnesium values even by two and a half hours were approximately 300 per cent higher than previous to the dosing-a level of blood magnesium never before observed so quickly after oral dosing. Similar results were obtained from both sheep, and by four hours after dosing the blood magnesium had reached 15.4 mg. and 10.0 mg. per 100 ml. of serum for sheep 7 and 8 respectively. The importance of this result in magnesium therapy would appear to be very great, but many aspects must be examined before suggesting its use in either the cure or prevention of hypomagnesaemia or in other diseases where magnesium salts are prescribed. Unfortunately, probably due to the very quick absorption of the salt, little could be deduced as to the part of the alimentary tract in which the absorption had taken place, except that in the case of sheep 8 there was obvious absorption of magnesium from the rumen. In both sheep 7 and 8 the phosphate content of the blood increased. The large dose of sodium dihydrogen phosphate given to sheep 9 and 10 increased the inorganic phosphate content of the blood to abnormal values, but the magnesium content was only slightly affected, falling from 3.26 to 2.58 mg. and 3. I 7 to 2.64 mg. for 9 and 10 respectively. The large dose of phosphate had a much greater effect on the blood calcium which fell in both sheep to an extremely low level. The dose of 4 oz. calcium chloride to sheep I I increased its blood calcium in two and a half hours to nearly twice its predosing level, and absorption of calcium was obvious from the rumen and abomasum. Both the blood magnesium and blood phosphate were only slightly increased by the large dose of calcium chloride. In all sheep, 9, 10 and I I, absorption of magnesium was apparent from the rumen. Many research workers in the field of mineral metabolism have suggested that the metabolic pathways of calcium and magnesium are different, and the above results would tend to support this view for ruminants. Absorption of Magnesium from the Various Parts of the Alimentary Tract Since the results from the experimental technique described in the previous section were not conclusive, another series of experiments was undertaken in which absorption of magnesium from each part of the alimentary tract was studied in turn. For this purpose the tract was divided into three sections-rumen and abomasum; duodenum and small intestine; and caecum, colon and terminal colon.
Blood
Ca. mg.%
Mg. mg.%
mg . o~
P.
9 ' 7'
9'45 9 ' 18
9' 18
9 '05 9'05
8'9 2
9 '05 8 ' 78
9,60
9 '45 ) 15 '40
Rumen Abomasum
Carotid 2
Duodenum Int estine
Carotid 3
Caecum Colon Terminal Colon
Carotid 4
Jugular 3
2i-3 hrs, after
hrs, after
4 hrs. after
til
-
3 ~ -4
-
---
3i hrs. after
- - - ----
3- 3! hrs. after
3 hrs. after
- - -- - --
8 '05 8'95
10 '53
2 '50 8'70
9 '26 9. 80
9.6 8'0
Ca. mg,%
M g.
3 2' 6 3'03
8'25 19'75
3'17 2' 79
7.6 7,6
7.6
8'78
8'7 8 8'7 8
10,60
10 ,80 11'0
26 '75
28,65 44'75
2 '56
2,66 2'23
- - - - - - --
11 '90 9 '33 18 ·65 23 .68
2' 19 2 '54
6'12 9'46
mg.% mg.%
P. -~--Ca. Mg. P.
6·65 6 '3 8
3 '3° 2,81
19'5° 29'25 20'00 25 '39
2' 74 2 '47
8 '25 9 '32
- -1 - 1 - - 2,60 18 '50 23 '95 2'47 6 '38 9 '40 - -- --- - - - - - - - - - - - -
9.84 6'79
II
112 g. CaCI 2• 6H2O
Sheep
8'9 0
11'08
2'4 2
3°'85
6'25
2'3°
12'32
11'5
2'34 2'3 0
11'46
2'3 2
2 '5 0 2'48
7'2
6,8 6·8
6 '25 5'99
3 1.65
5' 85
'20 11'20
15'7°
8'00
8'13
13'7
-
lI'go
2'58
2'5 8
6'53
10'00
10'70
6~~1
1- - - - - -
10'26
I I
2'32
2·64
2'9 6 2'63
9 '5 2
22 '00 23'95 23 '5 0 23'14
21 '25 22 '74
2'23
9 '3 2
2 '33
2 '55 2 '14
9' 26
10' 16 9.83
--- - - -- - - - - - - - - -
21 ·65 20 '47
23 ' 15 23 '4° 22 '20 22'46
9.66 g,80
- - - ---
2·33 2'3 0
33 '05 1~ I ~4 23~15122 ,35~.31 _~ '96
35'" 5'59 ,,6, '3,80 '3,68 ~ ","" - - -------- - -
5'3 2
g'20 9'53
8 ,65 14 '30 8 '00 9'42 10'98 6'53 2'33 30 '60 - - - - - - '- - - - - - - -1-
12'7° 12'7°
2' 38 2'33
- - - - - - - - - - -I-
3 2 '5° 3°'35
2'47
- - -I - - -
19'75 23'95
- - - - - - -- - - - - - - - - - - - - - - - ----
9.87
7'2 7,6
- -- I - - - - -
11'08 11'08
5' 8 5 5'99
8 ,65 8'7 8
- -- -
9'3° 9'53
30 '60 3 1'65
11'9 11·6
- - - - - - - --
8 '78
- - - I ---- -
11 '43 11 ' 77
- - - - - - - - - - -- - - - - - - - - - - - - - - - - -- - - - -
11'43
- - - - - - - - - - - - - - - - - - - - - - -- - - - - - - - - - - - - - - - - - - - - -
10'77 10 '97
8'0
9 '45 8'9 0 10 '74 --- - -- --- 10'70 9'45 10'26 10'go 11'20 7'05 8'4 2 16'30
9 '96
--- - - - - - - - - --
I
Carotid
2! hrs. after
2 '47 10'00
10'40 9'45
10
12g.NaH! PO,.2H2O
- - - -- - - - - - - - - - - - - - - -- - - - - - - - --
9 '7 1 9'71
Jugular I Jugular 2
Before Dosing
- - - -- -- - - --
--,-'--
I
Sheep
mg,% mg.% _. ---------- - - - -mg,~ P. mg. %
1I2g. NaH2 PO, 2H2O
- - - ------
Sheep 9
Ca. Mg. P. Ca. Mg. ;;J~mg.% :::..g.% mg.% mg. % mg.%
[[2 g. Mg (N0 3h
[[2 g. Mg (N0 3h
- - 1 - -1-
Sheep 8
Sheep 7
- - - - - - - - --- - - - - - - - - - - --
Time 0] fIlmpling
TABLE 3
AllSORPTION OF MAGNESIUM FROM ALIMENTARY TRACT AFTER DOSING WITH VARIOUS SALTS
VI
t;;
tl
o o
s::
~
!'l
tl
z
:>
..,~
~
';-<
16
ABSORPTION OF MAGNESIUM FROM THE ALIMENTARY TRACT
The same operational procedure was carried out but cannulae were inserted in the section under investigation and the dose of magnesium sulphate was inserted by the cannula after pre-samples had been taken from the jugular vein, carotid artery and veins draining the particular section. At definite intervals after dosing further samples were taken from the veins and carotid artery. For each part of the tract samples of the contents were also withdrawn, via cannulae, after each bleeding in the case of at least one sheep. For the discussion of the results from this section the data have been tabulated to show more clearly the arterio-venous difference. Rumen and abomasum. Sheep 12 and 13 were given I 12 g. of magnesium sulphate into the rumen and sheep 14, 60 g. into the abomasum. In the case of 13 and 14 the contents of the rumen and abomasum respectively were regularly sampled. An attempt was made to mix the contents as thoroughly as possible by injecting the dose into as many parts of the section as possible through the TABLE 4 ABSORPTION OF MAGNESIUM FROM RUMEN AND ABOMASUM Concentration of Magnesium mg/loo rol.
Sheep Time after dosage (mins) Predosage 0-20 20-40 40--60 60-90 90-120 120-180
12 (II2
Carotid artery
Rumen vezn
ArterioVenous difference
1,82 2'28 2'28 2,84 2,69 2'9 8 3'3 0
1'99 3'23 3,62 2'9 2 2'97 3'15 3'77
+0'17 +0'95 +1'34 +0'08 +0'28 +0'17 +0'47
Sheep 13 Predosage 0-20 20-40 40--60 60-90 90-120 120-180
g MgSO. per rumen)
2,63 3'56 3'27 4'14 4'14 4'98 5'68
2'7 8 4'04 4,64 4,64 6'00 6'06 7'3 2
(II2
Arterio- I Rumen Abomasum Venous Abomasum vein contents difference contents
-
-
2'01 2'73 3'48 2'3 8 2'97 3'23 3,66
-
+0'19 +0'45 +1'20 -0'46 +0'28 +0'25 +0'3 6
-
-
-
-
-
g MgSO. per rumen) +0'15 +0'48 +1'37 +0'5 0 +1,86 +1'08 +1,64
12 1140 974 648 78 5 480 177
.-
-
-
-
-
-
-
-
I
-
-
I
-
I
-
I
I
-
-
-
Sheep 14 (60 g MgSO.per abomasum) Predosage 0-20 20-40 40--60 60-90 90-120 120-180
3'05 4'13 4'13 4'94 6'28 6,62 6'5 0
-
-
-
-
-
-
-
-
-
-
-
-
-
-
3'08 4'40 6'16 6,66 6,84 7'02 7'12
I
+0'03 +0'27 +2'03 +1'7 2 +0'5 6 +0'40 +0,62
I
16 1078 845 888 534 4 69 421
J.
STEWART AND E. W. MOODIE
17
cannula, and the same care was taken in the subsequent sampling of the contents. The results are given in Table 4. In both 12 and 13 the blood from the rumen vein had always a higher magnesium content than that of the immediately succeeding sample from the carotid artery, thus showing that absorption of magnesium had taken place from the rumen. From the analysis of the rumen contents it is observed that twenty minutes after dosing the concentration of magnesium was about 100 times greater than before the dose was given and that the concentration fell in three hours to ten times the pre-dosing concentration, yet at the end of three hours absorption was apparently taking place more quickly than immediately after dosing. This may have been due to the mucosa of the rumen being in more intimate contact with the magnesium sulphate as the experiment progressed, although the concentration of magnesium within the rumen had decreased. From the results of both 12 and 14, where in the one case the dose was given into the rumen and in the other into the abomasum itself, there is evidence of absorption of magnesium taking place from the abomasum; especially is this true one hour after dosing. The dose increased the concentration of magnesium in the abomasum of 14 very considerably and, just as in the case of the rumen injection, absorption took place even after the concentration was reduced, presumably by passage further along the tract. It is concluded from these experiments that magnesium can be absorbed from both the rumen and the abomasum when a large dose of magnesium sulphate reaches that section of the alimentary tract. Duodenum and small intestine. A similar technique was used for the duodenum and small intestine, cannulae being fixed in both and a dose of magnesium sulphate inserted via the cannulae. With the first sheep the dose inserted in the duodenum was I 12 g. magnesium sulphate, but the animal died 30 minutes later with the blood magnesium raised to 19.05 mg./lOo ml. serum and the calcium content 9.6 mg./lOo ml. Two further sheep, given 50 g. magnesium sulphate by intestinal cannula, died within 30 minutes and each had a blood magnesium of 20 mg./lOo ml. In all cases the magnesium/calcium ratio in the serum was 2: I. Allcroft (1947) found that after 90 g. magnesium sulphate given intravenously to a goat had raised the blood magnesium to 20.5 the goat died, the magnesium/calcium ratio being 2.5: I. Another goat given 90 g. magnesium sulphate subcutaneously died after seven hours with blood magnesium raised to 20.7 mg. and the magnesium/calcium ratio again 2.5: I. In the present experiments death ensued when the magnesium/calcium ratio reached 2: I which is in agreement with the experimental results of workers using non-ruminant animals. Sheep 15 and 16 were given 20 g. magnesium sulphate by duodenal cannula. Sheep 15 was selected as it had an extremely
18
ABSORPTION OF MAGNESIUM FROM THE ALIMENTARY TRACT
low blood calcium and high magnesium. Sheep I7 and 18 were given 5 g. magnesium sulphate, I7 by the duodenum and 18 by TABLE 5 ABSORPTION OF MAGNESIUM FROM DUODENUM AND SMALL INTESTINE Concentration of Magnesium mg/loo rol.
Sheep IS (20 g lvfgSO, per duodenum) Time after dosage (mins)
Predosage 0-3 0 30 - 60 60-120 120-180
I Carotid artery I 4. 14
ArterioDuodenum reno us Duodenum Intestine vezn difference contents vein
4. 17 8-61 7-48 7- 17 7-4 8
6-65 6-81 6-81 7-35
---+0·03 +1-96 +0- 67 +0-35 +0- 13
-
-
I
I
-
4-3 0 6-72 8-45 6-84 8-79
Arterio-
Intestine contents
veTlOUS
difference
-
+0-16 +0-07 +1- 6 4 +0-03 +1-44
-
-
-
Sheep 16 (20 g MgSO, per duodenum)
Predosage 0-3 0 3 0- 60 60-120 120-180 180-240
2-79 4- 09 3-82 4- 09 3-34 3- 2 5
I
2-95 8- 15 y 29 3-82 4- 23 4-7 0
I
+0-16
I +4- 06 II +1-47 -0-17
+0-89
I
-J- 1-45
--
-
2-54 3-92 3-98 3-9 2 4- 25 Y5 1
-0- 24 -0- 17 +0-16 -0- 17 +0-9 1 +2-26
-
-
I
-
Sheep 17 (5 g MgSO, per duodenum)
Predosage 0-3 0 30-60 60-120 120-180 180-240
3- 25 3- 25 3-73 4- 23 4- 8 7 4-7 2
3- 10 3-3 8 3- 60 4- 06 4-3 2 yoo
I
-0- 15 +0- 13 -0- 13 -0-17 -0-55 +0-28
-
5 212 221 64 25 18
-
-
I
-
I
-
I
-
-
-
Sheep 18 (S g MgSO, per small intestine)
Predosage 0-3 0 30-60 60-120 120-180 180-240
3-75 3- 8 4 4-3 6 4- 12 4- 12 4- 17
-
I
-
--
3-05 4-55 4-7 2 4-74 4- 15 4- 17
-0-70 +0-7 1 +0-36 +0-62 +0-03
-
I
24 6g6 2g8 25 8 28 3 206
the small intestine. The usual operational procedure was carried out in each animal and the results are shown in Table 5. In the case of both 15 and 16 there was obvious absorption from the duodenum within 30 minutes of dosing, the magnesium content of the blood of the duodenal veins being 8.61 and 8.15 mg. with an arterio-venous difference of + 1.96 and +4.06 respectively. As the salt passed from the duodenum to the small intestine it was very clearly shown in both sheep that absorption from the duodenum was reduced and absorption from the small intestine was increased,
J.
STEWART AND E. W. MOODIE
until a t the end of the p eriod the magnesium contents of the blood from the small intestin e v eins were 8.79 and 5.5 1 mg. as compared with 7-48 and 4.70 mg. for the duodenum vein. Absorption of m agn esium was not so clearly d emonstrated in th e case of sheep 17 a nd 18 after the smaller doses of 5 g. m agnesium sulphate, a lthough the concentra tion of magnesium in both duodenum and small intestine was about 50 times the pre-dosing concentration. Caecum and colon. In one of the a nimals only (sheep 3) mentioned in the first section the values for the veins d raining the caecum, colon a nd terminal colon (Table I), had suggested that a bsorption might be occurring. in that area of the alimentary tract, but it was d ecid ed to obtain m ore d ata. 50 g. of m agnesium sulphate were given to 19, and 20 g. to 20 by means of a caecal cannul a . From 20 caecal contents were taken as well as blood samples. Difficulties TABLE 6
ABSORPTI ON OF MAGNESIUM FROM CAEC UM Concentrati on of Magnesium mg/roo ml.
-- ......
Sheep 19 (50 g MgSO, per caecum) - -~
----~
I
Time after dosage (mins)
Carotid artery
Caecum vein
Pr edosage 0- 30 30-60 60- go gO- '20 '20- '5 0
2 °47 2°47 2"7 8 3° 2 ' 3"25 3"7 2
2 027 2"60 2 °6 7 3"08 3"3 0 3"62
Arterio- Caecum C01lvenous dijference tmts
- -
Sheep
Predosage 0- 30 3 0 - 60 60- go gO- ' 20 '20-'5 0 ' 50-'SO
2 °7 6 4 "35 8"05 7",8 6"67 6°7 2 6"4 0
I
I
2 °8 4 ' g"66 ' 7"6, 10"50 6 °g1 6 0g' 6 °57
-
- 0°20 + 0" ' 3 - 0°" - 0"23 + 0"05 - 0 "'0 20 ( 2 0
I++' O"oS 5" " I
+ 9 "55 + 3 "3 2 + 0 "24 +O "' g + 0" '7
-
-
-
I i
Colon blood
Arteriovenous difference
2 "22 2 °48 2"48 3"00 3° 29 3° 8 4
- 0 02 7 +0 00 ' -0"30 - 0"2' + 0"04 + 0 °' 2
I
Terminal Arteriocolon venous blood dijfermce
- --2 "49 2 "4 9 2"65 3"40 3"33 3"6 ,
-t-O'02
I
+0°02 --0"'3 +oo'g +0°08 -0""
g AlgS0, per caecum)
53 5S0 6 7 3 777 600 4 64 4 10
-
-
I
-
-
I
-
-
-
-
-
-
-
I
-
I I
I
I I
-
in sampling the colon owing to the solid nature of the contents prevented the injecting of salts into that part or into the terminal co lon" The results from 19 and 20 are given in Table 6" The increased content of magnesium in the final blood samples showed that absorption of magnesium must h ave taken place from the caecum or the colon since there was no chance of the salt percolating back to the small intestine, but in the case of 19 the blood from caecal, colon a nd termina l colon veins had a slightly higher content of magnesium than that of the caroti d artery in only one or two instances. On the other hand 20 showed very
20
ABSORPTION OF MAGNESIUM FROM THE ALIMENTARY TRACT
rapid and very large absorption from the caecum. By 30 minutes after dosing the caecal vein sample had a magnesium content of 19.46 mg. with an arterio-venous difference of + I 5..l I. Throughout the three hours of the experiment an exceedingly high magnesium content was maintained in the caecal blood. The marked difference in the values for 19 and 20 is difficult to understand unless in the case of 20 the dose, though less in quantity, may have been added to a much less total volume of caecal contents or may have been placed in much closer contact with the mucous membrane. As was evident from the results of the first section every animal receiving a dose of magnesium sulphate had a much higher blood phosphate at the end of the experiment than at the beginning, irrespective of where in the alimentary tract the salt had been added. Comparison of Table 7 with Table I shows that in most cases the rise in blood phosphate was much higher after magnesium dosage than after total anaesthesia or simple operation without additional TABLE 7 ALTERATION IN CALCIUM AND PHOSPHORUS CONTENT OF BLOOD IN JUGULAR VEIN DURING COURSE> OF EXPERIMENT mg/IOO ml.
Sheep No. 12. 13. 140 15. 16. 17. 18. 19. 20o
Dose
12 g. MgS04 per rumen .° 2 g. MgS04 per rumen °° 60 go MgS04 per abomasum 20 go MgS04 per duodenum 20 go MgS04 per duodenum 5 go MgS04 per duodenum ° ° 5 g. MgS04 per small intestine 50 g. MgS04 per caecum °° 20 g. MgS0 4per caecum °° I
I I
Calcium mg/roo ml
I
Inorganic phosphorus mg/roo ml
Before dosing
End of experiment
Before dosing
10 °7 8 10 °7 0 9°33 5°45 9° 60 10°10 9°90 10.70 9. 10
9° 18 9°7 0 9°3 0 4°7 8 10 °90 9°3 0 9°3 0 9.60 9° 20
7° 80 6°29 5"94 9°96 8 060 5"94 8 028 7° 80 7°3 6
I
End qf experiment 8 °9 6 10°60 11 080 14° 04 15° 10 10 °9 2 13°40 11.30 11·20
I
magnesium being given. In no case, however, was it possible to ascertain if absorption of phosphate had taken place from any specific part of the alimentary tract. Moreover it was confirmed that the increases in the magnesium and phosphate contents of the blood were not proportional. From the present series of experiments it was impossible to determine whether the large doses of magnesium sulphate had directly influenced phosphate absorption from the alimentary tract or whether the large increases in phosphate content of the blood as the operation proceeded were exaggerated effects of the operational procedure although the values in Table I would tend to show that the manipulation of the tissues during operation did not seriously affect the blood phosphate level. Table 7 also shows that
J.
STEWART AND E. W. MOODIE
21
the calcium content of the blood tended in most cases to fall slightly. This fall could not be correlated with the very substantial rises in magnesium content of the blood after magnesium sulphate had been given. Thus from the above two series of experiments it is concluded that under certain circumstances magnesium may be absorbed from the rumen, abomasum, duodenum, small intestine and caecum, and apparently in largest amounts from the duodenum and small intestine. CONCLUSIONS
Experiments have been carried out on anaesthetised sheep to discover in what parts of the alimentary tract absorption of magnesium takes place. Venous blood from the right ruminal, left gastric, gastro-duodenal and anterior pancreatic-duodenal, intestinal, caecal and colic branches of the ileo-caeco-colic and left colic veins was taken by syringe at different intervals after the introduction of magnesium salts by mouth or through cannulae. These blood samples, which were considered to be representative of drainage from the various parts of the alimentary tract, were checked against arterial blood taken from the carotid artery at comparable intervals. It was shown that after heavy doses of magnesium sulphate under certain circumstances, absorption of magnesium may take place from the rumen, abomasum, duodenum, small intestine and caecum. The principal site of magnesium absorption is probably the duodenum and small intestine. After large doses of magnesium salts the phosphate content of the blood was also increased but the calcium content was slightly decreased. There was no evidence to show that calcium and magnesium followed a similar pathway of metabolism. It was also shown that magnesium was much more quickly and efficiently absorbed after doses of magnesium nitrate by mouth than after similar amounts of magnesium sulphate. The importance of this in veterinary medicine has yet to be studied. REFERENCES
Allcroft, W. M. (1947). Vet. J., 103, 157. Masson, M., and Phillipson, A. T. (1951). J. Physiol., 1I3, 18g. Parathasarathy, D., Garton, G. A, and Phillipson, A T. (1952). Biochem, J.,52, XVI. Scarisbrick, R., and Ewer, T. K. (1951). Ibid., 49, LXXIX. Schambye, P. (1951). Nord. vet. Med., 3,555. [Receivedfor publication, April 12th, 1955]
10
COMPo PATH.
1956.
VOL.
66.
THE ABSORPTION OF MAGNESIUM FROM THE ALIMENTARY TRACT OF SHEEP By
J.
STEWART
Moredun Institute, Gilmerton, Edinburgh
and
*E. W.
MOODIE
Royal (Dick) School qf Veterinary Studies, Edinburgh INTRODUCTION
There is still much controversy regarding the cause of seasonal hypomagnesaemia and hypomagnesaemic tetany in both cattle and sheep, and a survey of the literature reveals that little or nothing is known regarding the absorption of magnesium from the alimentary tract of ruminants. The following experiments, therefore, were carried out as a preliminary to the study of the factors influencing magnesium absorption and to ascertain if possible the region of maximum absorption. Sheep were selected as the most useful animals for the operational procedure and manipulation. They were not allowed food for the twelve hours preceding operation and at the end of each experiment were killed whilst still under anaesthesia. OPERATIONAL PROCEDURE
Anaesthesia was induced and maintained by the use of Pentobarbitone Sodium Solution (I gr. per m!.) given intravenously. The experimental animal was placed on a heated operating table and the abdominal cavity was opened by an incision made in the right flank through the skin, abdominal muscles and peritoneum from a point at the edge of the last lumbar transverse process to the region of the xiphoid cartilage. Blood samples were taken from the jugular vein immediately preceding dosing and after completion of the operation to observe the changes in the mineral concentration of the venous blood during the course of the procedure. Prior to, and at intervals during, the operation samples were taken from the carotid artery to represent arterial blood. Blood was also taken from the following veins to represent drainage from the various parts of the alimentary tract-right ruminal to indicate drainage from the rumen, left gastric from the abomasum, gastro-duodenal and anterior pancreatico-duodenal from the duodenum, intestinal from the intestine, caecal branch of the ileo-caecal-colic from the caecum, colic trunk of the ileo-caecal-colic from the colon, and the left colic to represent drainage from the terminal colon. In one series of experiments samples of the contents of the various parts of the alimentary tract were taken at the same time as the blood samples representing drainage from these parts. This was done by means of cannulae inserted at the time of operation. The cannulae used for the rumen and caecum had an external diameter of 3 cm. and an internal *Now of Queensland Veterinary School, Yeerongpilly, Brisbane, Australia.
J.
STEWART AND E. W. MOODIE
I I
diameter of 1.25 cm. while those used for the small intestine and abomasum had an external diameter of 8 mm. and an internal diameter of 5 mm. Both blood and alimentary tract contents were assayed for calcium, inorganic phosphorus and magnesium-calcium by the Kramer-Tisdall oxalate precipitation and permanganate titration method, magnesium by a modification of the Denis method, and phosphorus by the Fiske and Subarrow method. RESULTS
Abs01ption of Magnesium Throughout the Alimentary Tract In the present work it was assumed that, if the concentration of an element in the blood from the vein draining a part of the alimentary tract was significantly higher than that of the succeeding sample from the carotid artery, absorption had taken place from that part. Objection to this assumption might be raised if there was a long interval between the taking of the venous and arterial samples, but in the present work the interval was very brief, being only of a few minutes' duration. The value for venous blood was always compared with the value of the succeeding carotid sample. Great care is necessary in the interpretation of the data and the general trend of values in the contents of both the venous and carotid samples must be examined as well as the values for the contents of the various parts of the alimentary tract under consideration. This method has been adopted by most of the workers in this field of ruminant physiology (Masson and Phillipson, 1951; Parathasara thy, Garton and Phillipson, 1952; Schambye, 1951; Scarisbrick and Ewer, 1951). In order to ascertain whether the anaesthetic would have an effect on the blood minerals under examination two sheep, A and B, were anaesthetised and kept under total anaesthesia for four hours, samples being taken at intervals from the jugular vein. Two sheep, C and D, were kept in the same pen but not anaesthetised and were bled at similar intervals to A and B. It will be seen from Table I that anaesthesia had very little effect on the blood calcium, magnesium and inorganic phosphate, a greater variation being apparent in C and D than in A and B. In the case of sheep I, 2 and 3 the operational procedure was carried out to ascertain if the manipulation of the animals, consequent on the technique employed, would exert a greater effect on the blood minerals than that of total anaesthesia, as shown in A and B. From Table 1 it was seen that the procedure had little effect on either blood calcium or magnesium, although there was a slight variation in the contents of the various veins sampled. The variation in the phosphate content of the veins was greater than that of the calcium-and magnesium, but there was no evidence of any serious alteration due to tissue response after manipulation. Much has been written regarding the diurnal variation of blood phosphate but the data in Table I showed little change over three or four hours.
12
THE ABSORPTION OF MAGNESIUM FROM ALIMENTARY TRACT
From the data of Table I it was also apparent that little could be d educed regarding the site of magnesium absorption. There \vas TABLE
I
EFFECT OF THE ANAESTHETIC AND OF THE OPERATIONAL PROCEDURE ON THE BLOOD MINERALS
I
Anaestlutised
No anaesthetic
C- - --
- - - - ---S-he-ep-A--, Sluep B --Sheep Sheep -n -mg/lOo ml mg/roo ml mg/roo ml mg/roo ml Time - Mg pC;; Mg - p-C;; Mg ' -PC;; Mg -P-iCa
1-
-P-re--1T s ! hr 8'5 8'5 I " 8'5 2 " 8 '5 3 " 8'3 4 "
3'38 3'38 3'35 3'3 1 3 '2 9 2,81
6'54 5'74 5'54 5'90 5'74 5 '54
~ 2'40 10'1 10' 1 10'0 10'2 10'1
------ ----- - Jugular
I
, •
Carotid
I
.'
~
~
p
9,6
1,89
4'04
~~ 9,6 8'5 9'9 8'5 g'l 9'9 8'1
2'09 2 '01 1,87 1,86 2'27 1'75 2'01
1--=-1 -
2 '44 2'44 2 '44 2 '48 2'42 2'12
Is.;- ~ 2 ' 38 9 ' 26 7'56 7'40 7' 26 6'76
10'9 10 ' 9 10'9 11'2 11'2
~
~
~
9'1
2'34 4'50
p
5'26
4'71 7'14 8,85 5'40 5'40 5' 13 7'25
4'97 4 ' 97 4,68 5'60 5'52 4'97 5'88
-
-J-U-gU-I-a-r-2----,-·--+I--I --=-I ~
-;;;-:36 9,80 9'26 9'52 9,80 8'70
Sheep 3 mg/ roo ml serum
- -, - --. ----11-
1-
2'78 2 4' 0 2 '3 6 1 2'271' 2'03
Sheep 2 mg/roo ml serum
5,62 --;.;- 2'24
------------I--~i-
Carotid 2
10'9 10'9 10'9 10'9 10'9
Sheep r mg/lOo ml serum
Blood sample
Rumen Abomasum Duodenum Intestine Caecum Colon Terminal colon
~
6'10 2'41 6 ' 23 2'42 6'4 1 2'40 6'28 2'40 6'30 2'38 6'10
8,8 9'1 9'0 9'1 9'1 9'9 8,8
2'08 2'18 2'17 2'21 2'22 2'29 2'24
-
11'3
'-
-
;- -
~ I
p
--1- 3'03
I 3,88
~~I-;8~ 10'9 11 ' 1 11'1 10'4 10'4 9'7 11'3
---2 ,87 3 '14 3'56 3'29 3'56 3'21 3,80
4 '52 5,60 4'76 4,62 5'19 5' 8 4 6'02
~ 2'22~~~! --=9 ' 11 2 ' 3 0 5'40 1~~i~~
a remarkable constancy in the mineral content of all veins for any one animal and practically all the values were within the normal range for sheep. In order to increase the magnesium content along the whole tract 4 oz. (I 12 g.) of magnesium sulphate were given orally to three sheep, (4, 5 and 6) and two hours later operation was commenced. In the case of 6, samples of the contents of th e various parts of the alimentary tract were taken by cannulae as described above, but owing to the extremely solid nature of the contents of the colon and terminal colon it was not possible to obtain samples from these two regions. The results are shown in Table 2. Slight absorption of magnesium took place from both the rumen and abomasum of both sheep 4 and 6 and from the abomasum of sheep 5. This was true also of the duodenum and small intestine
J.
STEWART AND E. W. MOODIE
except in 6. It was apparent from the assay of the samples of the contents of the various parts of the tract that within the period TABLE
2
ABSORPTION FROM ALIMENTARY CANAL AFTER DOSING WITH 112 g_ MAGNESIUM SULPHATE
Timeo! sampling
I Sample
Pre-dosing Jugular Blood Jugular BIDDd 2 hrs. after dosing CarDtid Blood 2-2! hrs. after dDsing
2! hrs. after 2!-3 hrs. after dDsing
Rumen B1DDd Rumen CDntents Abomasum Blood Abomasum Contents Carotid BloDd Duodenum Blood Duodenum Contents Intestine Blood Intestine Contents
3 hrs_ after Carotid Blood
- -3-4 hrs. after dosing
Caecum Blood Caecum CDntents CDlon Blood Terminal Colon B1Dod
I
Sheep 4
Sheep 5
mg. per cent_
mg _per cmt
Cal
Mg.
P.
~1 2'32
Ca_
Mg.
'- P.
- - - - --
5"60. 10·66 2'39 5.67 10'4 3 -10 4'97 10'26 3.66 5'50.
- - - - - - - - - - -g·86
Jugular BloDd
mg_per cent P. Ca. Mg. -~-
- -- --
4- 17 7'50.
10. '0.
3'27
5"95
9-7
4-0.4
7-50. 10.-0.0. 4'5 1 7'08
g- I g'2
2'78 9'95 3'9D 8·60
g'l
3'9D 8'70.
------
- - - - - - - - - - - -- - - - - 10.-2 4'0.4 6'55 10'13 4· D9 7'0.2 9-3 5"53 9'35 -. - - - 27-0. 145-0. 50.'5_ 10. '0
-
--
-
-
3- 66 6'50. 9'78
- - - -I-
-
-
4' 19 6-88
g'6
5- 20.
7-70. 10 '43 5"4 2
-
9-3
4'93 -
8-05 10-40. 5"5 6 -
-
-
8 -5 5"66
-
7- 1 3
-
10'1
30. -0. 129-0. 35"2-
------
------ -
8 ·8
4 ' 28
8'5
4 ' 39 g-80
11'5
- ----
44- 0 143'0. Ig·6 8 -0. 4-4q 9'35 44 -0. 15 1'0. 17'7
- - - - - - - - - -- - - - - - -g-g 4'0.6 4.86 10.'10. 5'10 6·88
7'70.
9'73
7'9
4 -30. 10-45 10'26 5"5 6 6'9 2
7-9
- -- - - - - - -----8 -3 5"3 6 9'48 9'9 4-97 10'45 9'73 6-06 7'02 - - 93-0. 277-0 g' l
g-6D 5'4 2 6·84 4'97 - - --- - - - - - - - - - - - - - - - - 4 hrs. after Carotid BIDod
Sheep 6
g'2
10.' 1 8 -33 11 '20. g·86 6'4 1 8'40.
1~17.66~i~
5" 25
8-0. 5"22
9'24
-
-----8-3
5"22
8·0.
5"49 9'95
9-35
---------6-0.6 8'47 1
of the experiment, four hours, the dose of magnesium sulphate had passed to the caecum, but there was no real evidence of absorption from the caecum and colon of magnesium or of calcium and phosphate. As regards interaction of magnesium with calcium and phosphorus a point of interest is that whereas there was a slight fall in the calcium content of the venous and arterial blood there was a considerable rise in the inorganic phosphate contents, except in 6 which had a high phosphate content before the dose was given. In order to -see the effect of the magnesium ion the experiment was repeated using magnesium nitrate instead of sulphate, and so sheep 7 and 8 were given I 12 g. magnesium nitrate two and a half hours previous to the operational procedure. To ascertain the
14
ABSORPTION OF MAGNESIUM FROM THE ALIMENTARY TRACT
interaction of increased phosphorus and increased calcium intake on the magnesium content of the blood sheep 9 and 10 were given 112 g. sodium dihydrogen phosphate (NaH 2P0 4 .2H 20) and sheep I I was given 112 g. calcium chloride (CaCI 2 .6H 20). The analytical results are shown in Table 3. The most striking result from the dosage of magnesium nitrate was the much enhanced absorption of magnesium, as the blood magnesium values even by two and a half hours were approximately 300 per cent higher than previous to the dosing-a level of blood magnesium never before observed so quickly after oral dosing. Similar results were obtained from both sheep, and by four hours after dosing the blood magnesium had reached 15.4 mg. and 10.0 mg. per 100 ml. of serum for sheep 7 and 8 respectively. The importance of this result in magnesium therapy would appear to be very great, but many aspects must be examined before suggesting its use in either the cure or prevention of hypomagnesaemia or in other diseases where magnesium salts are prescribed. Unfortunately, probably due to the very quick absorption of the salt, little could be deduced as to the part of the alimentary tract in which the absorption had taken place, except that in the case of sheep 8 there was obvious absorption of magnesium from the rumen. In both sheep 7 and 8 the phosphate content of the blood increased. The large dose of sodium dihydrogen phosphate given to sheep 9 and 10 increased the inorganic phosphate content of the blood to abnormal values, but the magnesium content was only slightly affected, falling from 3.26 to 2.58 mg. and 3. I 7 to 2.64 mg. for 9 and 10 respectively. The large dose of phosphate had a much greater effect on the blood calcium which fell in both sheep to an extremely low level. The dose of 4 oz. calcium chloride to sheep I I increased its blood calcium in two and a half hours to nearly twice its predosing level, and absorption of calcium was obvious from the rumen and abomasum. Both the blood magnesium and blood phosphate were only slightly increased by the large dose of calcium chloride. In all sheep, 9, 10 and I I, absorption of magnesium was apparent from the rumen. Many research workers in the field of mineral metabolism have suggested that the metabolic pathways of calcium and magnesium are different, and the above results would tend to support this view for ruminants. Absorption of Magnesium from the Various Parts of the Alimentary Tract Since the results from the experimental technique described in the previous section were not conclusive, another series of experiments was undertaken in which absorption of magnesium from each part of the alimentary tract was studied in turn. For this purpose the tract was divided into three sections-rumen and abomasum; duodenum and small intestine; and caecum, colon and terminal colon.
Blood
Ca. mg.%
Mg. mg.%
mg . o~
P.
9 ' 7'
9'45 9 ' 18
9' 18
9 '05 9'05
8'9 2
9 '05 8 ' 78
9,60
9 '45 ) 15 '40
Rumen Abomasum
Carotid 2
Duodenum Int estine
Carotid 3
Caecum Colon Terminal Colon
Carotid 4
Jugular 3
2i-3 hrs, after
hrs, after
4 hrs. after
til
-
3 ~ -4
-
---
3i hrs. after
- - - ----
3- 3! hrs. after
3 hrs. after
- - -- - --
8 '05 8'95
10 '53
2 '50 8'70
9 '26 9. 80
9.6 8'0
Ca. mg,%
M g.
3 2' 6 3'03
8'25 19'75
3'17 2' 79
7.6 7,6
7.6
8'78
8'7 8 8'7 8
10,60
10 ,80 11'0
26 '75
28,65 44'75
2 '56
2,66 2'23
- - - - - - --
11 '90 9 '33 18 ·65 23 .68
2' 19 2 '54
6'12 9'46
mg.% mg.%
P. -~--Ca. Mg. P.
6·65 6 '3 8
3 '3° 2,81
19'5° 29'25 20'00 25 '39
2' 74 2 '47
8 '25 9 '32
- -1 - 1 - - 2,60 18 '50 23 '95 2'47 6 '38 9 '40 - -- --- - - - - - - - - - - - -
9.84 6'79
II
112 g. CaCI 2• 6H2O
Sheep
8'9 0
11'08
2'4 2
3°'85
6'25
2'3°
12'32
11'5
2'34 2'3 0
11'46
2'3 2
2 '5 0 2'48
7'2
6,8 6·8
6 '25 5'99
3 1.65
5' 85
'20 11'20
15'7°
8'00
8'13
13'7
-
lI'go
2'58
2'5 8
6'53
10'00
10'70
6~~1
1- - - - - -
10'26
I I
2'32
2·64
2'9 6 2'63
9 '5 2
22 '00 23'95 23 '5 0 23'14
21 '25 22 '74
2'23
9 '3 2
2 '33
2 '55 2 '14
9' 26
10' 16 9.83
--- - - -- - - - - - - - - -
21 ·65 20 '47
23 ' 15 23 '4° 22 '20 22'46
9.66 g,80
- - - ---
2·33 2'3 0
33 '05 1~ I ~4 23~15122 ,35~.31 _~ '96
35'" 5'59 ,,6, '3,80 '3,68 ~ ","" - - -------- - -
5'3 2
g'20 9'53
8 ,65 14 '30 8 '00 9'42 10'98 6'53 2'33 30 '60 - - - - - - '- - - - - - - -1-
12'7° 12'7°
2' 38 2'33
- - - - - - - - - - -I-
3 2 '5° 3°'35
2'47
- - -I - - -
19'75 23'95
- - - - - - -- - - - - - - - - - - - - - - - ----
9.87
7'2 7,6
- -- I - - - - -
11'08 11'08
5' 8 5 5'99
8 ,65 8'7 8
- -- -
9'3° 9'53
30 '60 3 1'65
11'9 11·6
- - - - - - - --
8 '78
- - - I ---- -
11 '43 11 ' 77
- - - - - - - - - - -- - - - - - - - - - - - - - - - - -- - - - -
11'43
- - - - - - - - - - - - - - - - - - - - - - -- - - - - - - - - - - - - - - - - - - - - -
10'77 10 '97
8'0
9 '45 8'9 0 10 '74 --- - -- --- 10'70 9'45 10'26 10'go 11'20 7'05 8'4 2 16'30
9 '96
--- - - - - - - - - --
I
Carotid
2! hrs. after
2 '47 10'00
10'40 9'45
10
12g.NaH! PO,.2H2O
- - - -- - - - - - - - - - - - - - - -- - - - - - - - --
9 '7 1 9'71
Jugular I Jugular 2
Before Dosing
- - - -- -- - - --
--,-'--
I
Sheep
mg,% mg.% _. ---------- - - - -mg,~ P. mg. %
1I2g. NaH2 PO, 2H2O
- - - ------
Sheep 9
Ca. Mg. P. Ca. Mg. ;;J~mg.% :::..g.% mg.% mg. % mg.%
[[2 g. Mg (N0 3h
[[2 g. Mg (N0 3h
- - 1 - -1-
Sheep 8
Sheep 7
- - - - - - - - --- - - - - - - - - - - --
Time 0] fIlmpling
TABLE 3
AllSORPTION OF MAGNESIUM FROM ALIMENTARY TRACT AFTER DOSING WITH VARIOUS SALTS
VI
t;;
tl
o o
s::
~
!'l
tl
z
:>
..,~
~
';-<
16
ABSORPTION OF MAGNESIUM FROM THE ALIMENTARY TRACT
The same operational procedure was carried out but cannulae were inserted in the section under investigation and the dose of magnesium sulphate was inserted by the cannula after pre-samples had been taken from the jugular vein, carotid artery and veins draining the particular section. At definite intervals after dosing further samples were taken from the veins and carotid artery. For each part of the tract samples of the contents were also withdrawn, via cannulae, after each bleeding in the case of at least one sheep. For the discussion of the results from this section the data have been tabulated to show more clearly the arterio-venous difference. Rumen and abomasum. Sheep 12 and 13 were given I 12 g. of magnesium sulphate into the rumen and sheep 14, 60 g. into the abomasum. In the case of 13 and 14 the contents of the rumen and abomasum respectively were regularly sampled. An attempt was made to mix the contents as thoroughly as possible by injecting the dose into as many parts of the section as possible through the TABLE 4 ABSORPTION OF MAGNESIUM FROM RUMEN AND ABOMASUM Concentration of Magnesium mg/loo rol.
Sheep Time after dosage (mins) Predosage 0-20 20-40 40--60 60-90 90-120 120-180
12 (II2
Carotid artery
Rumen vezn
ArterioVenous difference
1,82 2'28 2'28 2,84 2,69 2'9 8 3'3 0
1'99 3'23 3,62 2'9 2 2'97 3'15 3'77
+0'17 +0'95 +1'34 +0'08 +0'28 +0'17 +0'47
Sheep 13 Predosage 0-20 20-40 40--60 60-90 90-120 120-180
g MgSO. per rumen)
2,63 3'56 3'27 4'14 4'14 4'98 5'68
2'7 8 4'04 4,64 4,64 6'00 6'06 7'3 2
(II2
Arterio- I Rumen Abomasum Venous Abomasum vein contents difference contents
-
-
2'01 2'73 3'48 2'3 8 2'97 3'23 3,66
-
+0'19 +0'45 +1'20 -0'46 +0'28 +0'25 +0'3 6
-
-
-
-
-
g MgSO. per rumen) +0'15 +0'48 +1'37 +0'5 0 +1,86 +1'08 +1,64
12 1140 974 648 78 5 480 177
.-
-
-
-
-
-
-
-
I
-
-
I
-
I
-
I
I
-
-
-
Sheep 14 (60 g MgSO.per abomasum) Predosage 0-20 20-40 40--60 60-90 90-120 120-180
3'05 4'13 4'13 4'94 6'28 6,62 6'5 0
-
-
-
-
-
-
-
-
-
-
-
-
-
-
3'08 4'40 6'16 6,66 6,84 7'02 7'12
I
+0'03 +0'27 +2'03 +1'7 2 +0'5 6 +0'40 +0,62
I
16 1078 845 888 534 4 69 421
J.
STEWART AND E. W. MOODIE
17
cannula, and the same care was taken in the subsequent sampling of the contents. The results are given in Table 4. In both 12 and 13 the blood from the rumen vein had always a higher magnesium content than that of the immediately succeeding sample from the carotid artery, thus showing that absorption of magnesium had taken place from the rumen. From the analysis of the rumen contents it is observed that twenty minutes after dosing the concentration of magnesium was about 100 times greater than before the dose was given and that the concentration fell in three hours to ten times the pre-dosing concentration, yet at the end of three hours absorption was apparently taking place more quickly than immediately after dosing. This may have been due to the mucosa of the rumen being in more intimate contact with the magnesium sulphate as the experiment progressed, although the concentration of magnesium within the rumen had decreased. From the results of both 12 and 14, where in the one case the dose was given into the rumen and in the other into the abomasum itself, there is evidence of absorption of magnesium taking place from the abomasum; especially is this true one hour after dosing. The dose increased the concentration of magnesium in the abomasum of 14 very considerably and, just as in the case of the rumen injection, absorption took place even after the concentration was reduced, presumably by passage further along the tract. It is concluded from these experiments that magnesium can be absorbed from both the rumen and the abomasum when a large dose of magnesium sulphate reaches that section of the alimentary tract. Duodenum and small intestine. A similar technique was used for the duodenum and small intestine, cannulae being fixed in both and a dose of magnesium sulphate inserted via the cannulae. With the first sheep the dose inserted in the duodenum was I 12 g. magnesium sulphate, but the animal died 30 minutes later with the blood magnesium raised to 19.05 mg./lOo ml. serum and the calcium content 9.6 mg./lOo ml. Two further sheep, given 50 g. magnesium sulphate by intestinal cannula, died within 30 minutes and each had a blood magnesium of 20 mg./lOo ml. In all cases the magnesium/calcium ratio in the serum was 2: I. Allcroft (1947) found that after 90 g. magnesium sulphate given intravenously to a goat had raised the blood magnesium to 20.5 the goat died, the magnesium/calcium ratio being 2.5: I. Another goat given 90 g. magnesium sulphate subcutaneously died after seven hours with blood magnesium raised to 20.7 mg. and the magnesium/calcium ratio again 2.5: I. In the present experiments death ensued when the magnesium/calcium ratio reached 2: I which is in agreement with the experimental results of workers using non-ruminant animals. Sheep 15 and 16 were given 20 g. magnesium sulphate by duodenal cannula. Sheep 15 was selected as it had an extremely
18
ABSORPTION OF MAGNESIUM FROM THE ALIMENTARY TRACT
low blood calcium and high magnesium. Sheep I7 and 18 were given 5 g. magnesium sulphate, I7 by the duodenum and 18 by TABLE 5 ABSORPTION OF MAGNESIUM FROM DUODENUM AND SMALL INTESTINE Concentration of Magnesium mg/loo rol.
Sheep IS (20 g lvfgSO, per duodenum) Time after dosage (mins)
Predosage 0-3 0 30 - 60 60-120 120-180
I Carotid artery I 4. 14
ArterioDuodenum reno us Duodenum Intestine vezn difference contents vein
4. 17 8-61 7-48 7- 17 7-4 8
6-65 6-81 6-81 7-35
---+0·03 +1-96 +0- 67 +0-35 +0- 13
-
-
I
I
-
4-3 0 6-72 8-45 6-84 8-79
Arterio-
Intestine contents
veTlOUS
difference
-
+0-16 +0-07 +1- 6 4 +0-03 +1-44
-
-
-
Sheep 16 (20 g MgSO, per duodenum)
Predosage 0-3 0 3 0- 60 60-120 120-180 180-240
2-79 4- 09 3-82 4- 09 3-34 3- 2 5
I
2-95 8- 15 y 29 3-82 4- 23 4-7 0
I
+0-16
I +4- 06 II +1-47 -0-17
+0-89
I
-J- 1-45
--
-
2-54 3-92 3-98 3-9 2 4- 25 Y5 1
-0- 24 -0- 17 +0-16 -0- 17 +0-9 1 +2-26
-
-
I
-
Sheep 17 (5 g MgSO, per duodenum)
Predosage 0-3 0 30-60 60-120 120-180 180-240
3- 25 3- 25 3-73 4- 23 4- 8 7 4-7 2
3- 10 3-3 8 3- 60 4- 06 4-3 2 yoo
I
-0- 15 +0- 13 -0- 13 -0-17 -0-55 +0-28
-
5 212 221 64 25 18
-
-
I
-
I
-
I
-
-
-
Sheep 18 (S g MgSO, per small intestine)
Predosage 0-3 0 30-60 60-120 120-180 180-240
3-75 3- 8 4 4-3 6 4- 12 4- 12 4- 17
-
I
-
--
3-05 4-55 4-7 2 4-74 4- 15 4- 17
-0-70 +0-7 1 +0-36 +0-62 +0-03
-
I
24 6g6 2g8 25 8 28 3 206
the small intestine. The usual operational procedure was carried out in each animal and the results are shown in Table 5. In the case of both 15 and 16 there was obvious absorption from the duodenum within 30 minutes of dosing, the magnesium content of the blood of the duodenal veins being 8.61 and 8.15 mg. with an arterio-venous difference of + 1.96 and +4.06 respectively. As the salt passed from the duodenum to the small intestine it was very clearly shown in both sheep that absorption from the duodenum was reduced and absorption from the small intestine was increased,
J.
STEWART AND E. W. MOODIE
until a t the end of the p eriod the magnesium contents of the blood from the small intestin e v eins were 8.79 and 5.5 1 mg. as compared with 7-48 and 4.70 mg. for the duodenum vein. Absorption of m agn esium was not so clearly d emonstrated in th e case of sheep 17 a nd 18 after the smaller doses of 5 g. m agnesium sulphate, a lthough the concentra tion of magnesium in both duodenum and small intestine was about 50 times the pre-dosing concentration. Caecum and colon. In one of the a nimals only (sheep 3) mentioned in the first section the values for the veins d raining the caecum, colon a nd terminal colon (Table I), had suggested that a bsorption might be occurring. in that area of the alimentary tract, but it was d ecid ed to obtain m ore d ata. 50 g. of m agnesium sulphate were given to 19, and 20 g. to 20 by means of a caecal cannul a . From 20 caecal contents were taken as well as blood samples. Difficulties TABLE 6
ABSORPTI ON OF MAGNESIUM FROM CAEC UM Concentrati on of Magnesium mg/roo ml.
-- ......
Sheep 19 (50 g MgSO, per caecum) - -~
----~
I
Time after dosage (mins)
Carotid artery
Caecum vein
Pr edosage 0- 30 30-60 60- go gO- '20 '20- '5 0
2 °47 2°47 2"7 8 3° 2 ' 3"25 3"7 2
2 027 2"60 2 °6 7 3"08 3"3 0 3"62
Arterio- Caecum C01lvenous dijference tmts
- -
Sheep
Predosage 0- 30 3 0 - 60 60- go gO- ' 20 '20-'5 0 ' 50-'SO
2 °7 6 4 "35 8"05 7",8 6"67 6°7 2 6"4 0
I
I
2 °8 4 ' g"66 ' 7"6, 10"50 6 °g1 6 0g' 6 °57
-
- 0°20 + 0" ' 3 - 0°" - 0"23 + 0"05 - 0 "'0 20 ( 2 0
I++' O"oS 5" " I
+ 9 "55 + 3 "3 2 + 0 "24 +O "' g + 0" '7
-
-
-
I i
Colon blood
Arteriovenous difference
2 "22 2 °48 2"48 3"00 3° 29 3° 8 4
- 0 02 7 +0 00 ' -0"30 - 0"2' + 0"04 + 0 °' 2
I
Terminal Arteriocolon venous blood dijfermce
- --2 "49 2 "4 9 2"65 3"40 3"33 3"6 ,
-t-O'02
I
+0°02 --0"'3 +oo'g +0°08 -0""
g AlgS0, per caecum)
53 5S0 6 7 3 777 600 4 64 4 10
-
-
I
-
-
I
-
-
-
-
-
-
-
I
-
I I
I
I I
-
in sampling the colon owing to the solid nature of the contents prevented the injecting of salts into that part or into the terminal co lon" The results from 19 and 20 are given in Table 6" The increased content of magnesium in the final blood samples showed that absorption of magnesium must h ave taken place from the caecum or the colon since there was no chance of the salt percolating back to the small intestine, but in the case of 19 the blood from caecal, colon a nd termina l colon veins had a slightly higher content of magnesium than that of the caroti d artery in only one or two instances. On the other hand 20 showed very
20
ABSORPTION OF MAGNESIUM FROM THE ALIMENTARY TRACT
rapid and very large absorption from the caecum. By 30 minutes after dosing the caecal vein sample had a magnesium content of 19.46 mg. with an arterio-venous difference of + I 5..l I. Throughout the three hours of the experiment an exceedingly high magnesium content was maintained in the caecal blood. The marked difference in the values for 19 and 20 is difficult to understand unless in the case of 20 the dose, though less in quantity, may have been added to a much less total volume of caecal contents or may have been placed in much closer contact with the mucous membrane. As was evident from the results of the first section every animal receiving a dose of magnesium sulphate had a much higher blood phosphate at the end of the experiment than at the beginning, irrespective of where in the alimentary tract the salt had been added. Comparison of Table 7 with Table I shows that in most cases the rise in blood phosphate was much higher after magnesium dosage than after total anaesthesia or simple operation without additional TABLE 7 ALTERATION IN CALCIUM AND PHOSPHORUS CONTENT OF BLOOD IN JUGULAR VEIN DURING COURSE> OF EXPERIMENT mg/IOO ml.
Sheep No. 12. 13. 140 15. 16. 17. 18. 19. 20o
Dose
12 g. MgS04 per rumen .° 2 g. MgS04 per rumen °° 60 go MgS04 per abomasum 20 go MgS04 per duodenum 20 go MgS04 per duodenum 5 go MgS04 per duodenum ° ° 5 g. MgS04 per small intestine 50 g. MgS04 per caecum °° 20 g. MgS0 4per caecum °° I
I I
Calcium mg/roo ml
I
Inorganic phosphorus mg/roo ml
Before dosing
End of experiment
Before dosing
10 °7 8 10 °7 0 9°33 5°45 9° 60 10°10 9°90 10.70 9. 10
9° 18 9°7 0 9°3 0 4°7 8 10 °90 9°3 0 9°3 0 9.60 9° 20
7° 80 6°29 5"94 9°96 8 060 5"94 8 028 7° 80 7°3 6
I
End qf experiment 8 °9 6 10°60 11 080 14° 04 15° 10 10 °9 2 13°40 11.30 11·20
I
magnesium being given. In no case, however, was it possible to ascertain if absorption of phosphate had taken place from any specific part of the alimentary tract. Moreover it was confirmed that the increases in the magnesium and phosphate contents of the blood were not proportional. From the present series of experiments it was impossible to determine whether the large doses of magnesium sulphate had directly influenced phosphate absorption from the alimentary tract or whether the large increases in phosphate content of the blood as the operation proceeded were exaggerated effects of the operational procedure although the values in Table I would tend to show that the manipulation of the tissues during operation did not seriously affect the blood phosphate level. Table 7 also shows that
J.
STEWART AND E. W. MOODIE
21
the calcium content of the blood tended in most cases to fall slightly. This fall could not be correlated with the very substantial rises in magnesium content of the blood after magnesium sulphate had been given. Thus from the above two series of experiments it is concluded that under certain circumstances magnesium may be absorbed from the rumen, abomasum, duodenum, small intestine and caecum, and apparently in largest amounts from the duodenum and small intestine. CONCLUSIONS
Experiments have been carried out on anaesthetised sheep to discover in what parts of the alimentary tract absorption of magnesium takes place. Venous blood from the right ruminal, left gastric, gastro-duodenal and anterior pancreatic-duodenal, intestinal, caecal and colic branches of the ileo-caeco-colic and left colic veins was taken by syringe at different intervals after the introduction of magnesium salts by mouth or through cannulae. These blood samples, which were considered to be representative of drainage from the various parts of the alimentary tract, were checked against arterial blood taken from the carotid artery at comparable intervals. It was shown that after heavy doses of magnesium sulphate under certain circumstances, absorption of magnesium may take place from the rumen, abomasum, duodenum, small intestine and caecum. The principal site of magnesium absorption is probably the duodenum and small intestine. After large doses of magnesium salts the phosphate content of the blood was also increased but the calcium content was slightly decreased. There was no evidence to show that calcium and magnesium followed a similar pathway of metabolism. It was also shown that magnesium was much more quickly and efficiently absorbed after doses of magnesium nitrate by mouth than after similar amounts of magnesium sulphate. The importance of this in veterinary medicine has yet to be studied. REFERENCES
Allcroft, W. M. (1947). Vet. J., 103, 157. Masson, M., and Phillipson, A. T. (1951). J. Physiol., 1I3, 18g. Parathasarathy, D., Garton, G. A, and Phillipson, A T. (1952). Biochem, J.,52, XVI. Scarisbrick, R., and Ewer, T. K. (1951). Ibid., 49, LXXIX. Schambye, P. (1951). Nord. vet. Med., 3,555. [Receivedfor publication, April 12th, 1955]