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Effect of dihydrotachysterol on calcium absorption in uremia
Effect of Dihydrotachysterol on Calcium Absorption in Uremia By Michael
Kaye and S. Sagar
The effect of dihydrotachysterol on gastrointestinal absorption of calcium was studied in five undialyzed and five dialyzed patients with chronic uremia. Fecal calcium decreased and calcium
balance of the changes dialyzed
became less negative in nine ten patients; however, the were more marked in the patients.
A
S PREVIOUSLY SHOWN, dihydrotachysterolz (DHT), a compound very similar to vitamin DZ or calciferol chemically, has nonetheless different was noted the favorable rebiologic properties. I>2 Among these differences sponse of long-term dialysis patients with active secondary hyperparathyroidism due to chronic renal failure treated with this agent, whereas a similar dose of calciferol appeared ineffective. In the present study the external calcium balance was assessed in patients with chronic renal failure before and after administration of dihydrotachysterol. Those being treated by dialysis showed a considerably greater decrease in fecal calcium and a more positive calcium balance after DHT than the nondialyzed patients. MATERIALS
AND METHODS
Two groups of patients were studied. In those with residual renal function, Group I, there were five patients, and a total of seven studies were carried out. In Group II there were five patients stabilized on a chronic dialysis program. A single study was conducted on each patient. Collections of stool and urine were carried out in a metabolic unit supervised by a research dietitian and technician. Each patient received a diet as identical in calcium content and general nature as possible to that which the patient was consuming before admission. Two diets were employed and given on alternate days. These were prepared before the start of the study and a day’s diet of each was analyzed. Any medications being taken by the patients such as supplemental calcium or phosphate binders, are indicated in Table 1. These were continued in the same dosage as were the hemodialysis schedules. Kiil dialyzers were used with a dialyzate calcium of 6 mg/loo ml and no phosphate. None of the patients had received pharmacologic doses of vitamin D, but the patients on dialysis took a multivitamin tablet containing 400 units of Dz. In the three cases where DHT had previously been used, 5, 6, and 2 mo had elapsed, since it was discontinued until the beginning of the study. Chromic oxide was used as a fecal marker, 0.25 g 3 times daily with meals; all‘calculations for daily fecal excretion were based on this. Stool and urine were collected in individual pools and the duration of each pool and results obtained before and after DHT administration are shown in Tables 2-6. The equilibration period and the
From the Division of Nephrology, Department of Medicine, the Montrenl General Hospital, Montreal, Quebec, Canada. Received for publication November 29, 1971. Supported by USPHS Grant I”843-66-542 and Medical Research Council Grant MA-3224 for the Metabolic Unit. Michael Kaye, M.B., F.R.C.P. (C): Director, Division of Nephrology, Department of Medicine, the Montreal General Hospital; and Associate Professor, Department of Medicine, McGill University, Montreal, Quebec, Canada. S. Sagar, M.B., B.S.: Clinical Fellow in Nephrology, Department of Medicine, the Montreal General Hospital, Montrenl, Quebec, Canada, 7uly 7969-Tune 1971. Metabolism,
Vol. 21, No. 9 (September),
1972
815
I I I I
I II
II II II
II
MUL I MUL II CAN McM BAR I BAR II ROY GEN
DIS NAN PIT
LAW
34
49 35 53
65 66 76 72 46 46 59 26
Age
l
As calcium gluconogalactogfuconate t As calcium carbonate. * AS calcium gluconate.
I
I
Group
__
Name
_~_
(Sandor).
Chronic glomerulonephritis
Chronic glomerulonephritis Chronic glomerulonephritis Nephrosclerosis
Chronic pyelonephritis Chronic pyelonephritis Chronic pyelonephritis Polycystic disease Nephrosclerosis Nephrosclerosis Chronic glomerulonephritis Heretitary nephritis
Diagnosis
4.3
7.2 5.6 4.1
71.4 9.7 9.6 9.6
5.0 6.9 6.2 4.6 6.6 7.6 6.1 5.4
P mg/lOo ml
7.5 6.1 10.2 9.0 9.2 6.3 7.6 9.3
Ca mg/lOO ml
Serum
Table 1. Clinical Data on Patients
0.3
0.9 0 1.5
30
30 36 28
30
Clearance ml/min
4.1 3.4 2.7 22.4 7.2 6.1 2.6 0.9
Hours Dialysis, Weekly
Creatinine
176* mg Ca/day orally 660’ mg Ca/day orally Aluminum hydroxide 2 tabs/day 680’ mg Ca/day orally
1.Ot g Ca/day orally -
660’ mg Ca/day orally -
Medication
I
I
Mean
Mean
Mean
Mean
Mean
‘Percent
ROY
Mean BARII
BAR
McM
CAN
Mean MULII
MUL
Name
1 2
1 2
1 2
1 2
1 2
1319
530 1316 1322
435 1035 1098 1067 639 639 639 525 534
1028 1028 1028 379 377 378 378 435 434
1 2
1 2 3
take mwday
Pariod
dose absorbed.
6 8
7 6
6 7
7 6
7
7 7
No. Days
In-
Ca
1293
703 1217 1369
528 895 951 923 657 617 637 705 700
1000 1035 1018 564 595 612 590 538 518
Ca Stool mwday
Control
18
41 23 13
86 31 34 32 33 57 45 41 41
19 28 24 16 30 24 23 70 101
Ca Urine mwday
9
+8
+ -
76 60
-214
-179 +109 +113 +112 - 51 - 35 - 43 -221 -207
+
- 35 - 14 -201 -248 -258 -235 -173 -185
Balante mglday
65
45 61 69
68 52 34 43 58 53 56 47 43
38 29 34 59 63 43 55 56 79
Ca47*
4 3 5
7 7 7
7 7
7 7
4 7 4
7 6
7 7
NO. Days
4 5 6
4 5 6
4 5
4 5
4 5 6
5 6
4 5
Period
0.25 0.25 0.25
0.5 0.5 0.5
0.25 0.25
0.25 0.25
0.25 0.25 0.25
0.25 0.25
0.25 0.25
DHT mg/day
1323
351 1333 1322 1314
435 1011 1043 1027 639 639 639 525 204 325
379 435 434 435
1028 1028 1028 379 378
Ca Intake mwday
Table 2. Calcium Balance--Group
I
1184
574 1165 1170 1216
373 898 793 846 658 672 665 686 577 458
532 429 353 337
972 1007 990 519 545
Ca stool mwday
24
45 27 21 24
86 25 28 27 57 14 36 50 41 45
25 88 86 86
19 13 16 22 28
Ca Urine w/day
24
12
+115
70
73 +
74
51 67 -
97 42 37 40 25 32 29 40 47 68
54 94 100 -
50 51 51 50 57
Ca4”
-268 $141 +131
-t-68 j-222 j-154 - 76 - 47 - 62 -211 -414 -178
-
+
-178 - 80 -5
+ 37 +6 + 19 -162 -195
Balante mwday
DHT
57
33
54
19
42
+107
-
-
+
-j-l55
+
+
ABalante mgfday
$5
-l-6
-27
-3
+29
-1
+17
A Ca47’
LAW
PIT
NAN
DIS
GEN
7 7 7
7 7
7 7
7 7
10 7
1 2 3
1 2
1 2
1 2
1 2
Period
426 426 426 490 470 480 1095 1101 1098 876 879 878 1200 1200 1199 1200
lPercentdoseabsorbed.
Mean
Mean
Mean
Mean
Mean
Name
No. Days
Ca Intake mglday
481 510 475 493 1010 890 950 542 508 525 1332 1338 1127 1266
474 487
Ca stool mg/day
Control
3 2
3 2 3 1 3
-
17 17 17 26 17 22
w/day
Ca Urine
+ -
69 68
+148 +331 +369 +350 -133 -141
+ 85 +211
- 65 - 78 - 72 -46 - 22 - 35
w/day
Balante
65 46 56 62 39 50 46 55 50 46 52 49 12 63 62 46
Ca47’
7 6
7 8
7 7
7 12
10 10
No. Days
5 6
4 5
4 5
4 5
4 5
Period
0.25 0.25
0.25 0.25
0.375 0.375
0.25 0.25
0.25 0.25
DHT mgldw
Table 3.Calcium Balance-Group
1170
426 426 426 486 451 469 1095 1101 1098 879 878 879 1200 1140
Ca Intake mg/day
II
1041
896 879 888 481 464 473 1069 1013
434 371 403 323 121 222
Ca Stool mgfday
6
2 3 3 7 4
16 22 19 13 11 12
Ca Urine mg/day
+123
- 24 + 33 + 4 +150 +319 +235 4199 +222 +210 f396 +411 +403 +124 +I23
Balante mg/day
DHT
55
81 82 82 88 89 89 83 76 80 47 46 47 65 44
Ca47’
76
53
62
+191
+
+
+270
+
ABalante mglday
A
-kg
-2
+30
+39
+26
Ca47’
9 W
I
I
Mean
Mean
Mean
Mean
Mean
7 6
7 7
6 6
7 6
6 7
7 7 6
1 2
2
1
1 2
1 2
1 2
1 2 3
1 2
7 7
411
367
662 375 359
291 469 473 471 259 218 239 720 603
745 1074 1074 1074 690 690 690 659 869
664 402 419
298 314 306 361 354 365 360 292 290
-
P Stool mglday
160
487 170 150
401 529 575 552 517 532 525 474 499
180 260 230 257 342 315 305 440 361
P Urine mglday
Control
622 610 616 587 577 582 582 745 744
'Per cent dose absorbed.
ROY
Mean BAR II
BAR
McM
CANI
Mean MULII
MUL
Name
Period
No. Days
P Intake mg/day
13 93
-116
-285 -143 - 90
+ 53 + 76 + 26 + 51 - 86 - 60 - 74 -335 -233
+ +
+ 16 + 60 - 31 -119 - 98 - 83
+144
Balante mglday
65
45 61 69
68 52 34 43 58 53 56 47 43
38 29 34 59 63 43 55 56 79
Ca47’
4 3 5
7 7 7
7 7
7 7
4 7 4
7 6
7 7
No. Days
4 5 6
4 5 6
4 5
4 5
4 5 6
5 6
4 5
Period
Table4.Phosphorus
0.25 0.25 0.25
0.5 0.5 0.5
0.25 0.25
0.25 0.25
0.25 0.25 0.25
0.25 0.25
0.25 0.25
DHT mg/day
585 745 744 745 745 1080 1060 1080 691 689 690 859 401 517 592 447 419 398 421
622 610 616 587 582
P Intake mg/day
Balance-Group i
347 248 255 337 260 428 369 399 207 169 198 584 518 471 524 393 391 366 383
516 510 513 354 339
P Stool mg/day
352 362 560 560 501 524 592 556 589 661 615 535 490 450 492 120 110 130 120
220 355 288 309 395
P Urine mgjday
-114 +115 - 71 -152 - 36 +128 +119 +123 - 85 -161 -123 -260 -807 -404 424 - 66 -62 - 98 - 82
-114 -255 -185 - 76 -152
Balante mgjday
DHT
54 94 100 97 42 37 40 25 32 29 40 47 66 51 67 73 70
50 51 51 50 57
Ca47’
31
49
72
+
34
-139
-
+
-104
-
-265
AEialante mglday
A
i-5
i-6
-27
-3
f29
-1
f17
Ca47’
Mean
Mean
Mean
Mean
Mean
7 7 7
7 7
7 7
7 7
10 7
1 2 3
1 2
1 2
1 2
1 2
Period
667 693 690 565 534 550 771 759 765 654 640 a47 ii08 1112 1106 1109
511 324 418 278 236 257 1651 1286 1469 584 620 602 406 392 372 390
mglday
P
Stool
take
mglday
lPercentdoseabsorbed.
LAW
PIT
NAN
DIS
GEN
Name
No. Days
Control
P In-
55 47 51 2 14 30 15
29 28 29 45 31 38 -
P Urine mgfday
1-243 $242 +267 $255 -680 -527 -704 +215 +173 +194 +700 +706 4706 +704
f147 +341
Balante mgldaY
65 46 56 62 39 50 45 55 50 46 52 49 12 63 62 46
Ca47*
7 6
7 a
7 7
7 12
10 10
No. Days
II
354
0.25 0.25
0.25 0.25
771 759 765 a40 a48 a44 1108 1020 1064
5 6
4 5
4 5
0.375 0.375
563 464 514
0.25 0.25
4 5
276 254 265 212 155 la4 1241 1491 1366 605 594 600 320 388 687 687 687
0.25 0.25
4 5
P Stool mgldey
DHT mg/daY
Period
P Intake mg/day
Table 5. Phosphorus Balance-Group
26
27 45 36 26 21 23 33 18 26 38 14
P Urine
$684
+364 +3aa +386 +325 +2a6 $307 470 -732 -601 +202 +236 +216 +750 +618
Balante mg/day
DHT
55
al a2 62 aa a9 a9 a3 76 80 47 46 47 65 44
Ca47*
52
-
+
20
24
f103
+
+143
%VW
ABalante
*A
+9
-2
+30
$39
$26
Ca47’
x
15
16 16
792 752
712
771 816 794
l
627 506
365
613 743 776
33 207
380
36 11 25
Urine w/day
or per cent
Stool w/day
balance
Intake w/day
Per cent dose absorbed. TA is the net change in either
Group
I
15 16 16
Group II Groups I and II
Group I Group II Groups I and II Phosphorus
Calcium
NO. Days
Control
53
60 62 9
radioactive
+I32 $ 39
-
+ -
Balante w/day
Table 6. Mean Values
calcium
50 51
52
52 50 51
Ca47’
775 726
676
740 608 774
Intake m/day
554 466
376
736 605 672
stool w/day
and Phosphorus
absorption.
16 16
15
15 16 16
No. Days
for Calcium
28 223
416
37 10 24
Urine w/day
Balance
35 +193 + 78
Balance w/day
j-193 + 37
-120
DHT
71 64
56
56 71 64
Ca47’
-I- 61 2
-67
-t-45 +131 + 67
ABalance w/day
$21 fl3
$4
i-4 +21 $13
Ca47’
A
5
z
it
C
2
E
E
F i;
822
KAYE AND SAGAR
first pool after DHT administration
of 4-5 days duration have been excluded. Radioactive calcium absorption was measured by giving orally 10 /Ki 47Ca at 8:00 a.m. after overnight fasting. The solution did not contain carrier calcium but two so-ml washes with tap water containing 4 mg/IOO ml calcium were taken to rinse the container. Stools were collected as part of the balance for the following 7 days, and homogenized and weighed aliquots were counted in duplicate together with a suitably diluted standard of the administered 47Ca. The 47Sc counts were excluded by appropriate window settings. Clinical data on the subjects are shown in Table I. Analytical methods were similar to those described previ0usly.334The DHT used was kindly supplied by Dr. C. W. Birkett of Winthrop Laboratories as Hytakerol. This has been shown to be chemically and biologically similar to pure crystalline DHT.2 Several months after completing the balance study and stopping DHT, all subjects in Group II, three other long-term dialysis patients, and one patient with chronic uremia awaiting transplantation were given 47Ca intravenously. The excretion of the isotope in the stool was determined over the following 5 days.
RESULTS
Control
Period
The findings are shown in Tables 2 and 3 for calcium and Tables 4 and s for phosphorus, and summarized in Table 6. The mean calcium intake was similar in the two groups, being 771 mg/day for Group I and 816 mg/day for Group II. Urine calcium was slightly higher in those not yet being dialyzed as would be expected. In Group II, the calcium balance was slightly positive and slightly negative in Group I, +62 mg/day as compared with -80 mg/day. The difference could be mainly accounted for by the smaller fecal calcium in Group II. Radioactive calcium absorption was comparable and low in both groups. If the two groups were pooled and divided into those with calcium intakes above and below 800 mg/day, the balance was $-89 mg/day where the intake was in excess of 800 mg daily and -129 mg/day when it was below. Phosphorus intake in the two groups was similar in the control period. The mean balance was -53 mglday for Group I and +I32 mglday for Group II. The difference is due to the negligible urinary phosphorus loss in this group. As the losses by hemodialysis have not been allowed for, overall balance would be actually much less positive for Group II. DHT Period Calcium intake was similar to the control period; however, balance was now positive in all the Group II patients and negative in three of the Group I patients. When the change in calcium balance was calculated, ACa in Table 2, all balances became more positive with the exception of the two studies done on BAR. This change in balance was due to a mean decrease in fecal calcium of 138 mg/day in Group II and 75 mg/dav in Group I. The improvement in calcium balance after DHT in the nondialyzed patients is small and variable from patient to patient. This contrasts with the uniform and in some instances quite striking positive balance seen in the Group II dialvzed patients. If the two groups are pooled, the overall change in calcium balance was significant using the Wilcoxon rank test, p
unchanged
in Group
in Group II and was I. The pooled change was almost zero. The change in
CALCIUM
ABSORPTION
823
IN UREMIA
phosphorus balance in Group II was less than the change in calcium balance and the molar ratio nCa/nP was 1.66, which is similar to the Call’ ratio of hydroxyapatite. The 47Ca absorption followed the change in stable calcium absorption and comparison of n*sCa and A4’Ca gave a correlation coefficient r = 0.6547, p <0.05. *‘Ca intravenously The nine subjects excreted 7.8 F 1.2 per cent of the administered dose, range 4.7%-16.4%, in the stool over the subsequent 5 days. This is similar to our previous values of 7.2% for normal subjects and 8.1% for patients with uremia with a calculated endogenous fecal calcium of 2.3 and 2.6 mg/ kg/day for control patients and patients with uremia, respectively.5 DISCUSSION
It should be noted that the balance data reported for the dialyzed patients do not represent the total gains or losses because no account has been taken of the changes occuring during hemodialysis. However, with a dialyzate calcium of 6 mg/loo ml the net transfer of calcium across the dialyzer membrane is minimal if the plasma calcium is in the normal range.s As we were mainly interested in intestinal absorption, it was felt to be permissible to ignore the changes during dialysis. In the case of phosphorus as the dialyzate is phosphate free and losses of 0.5-1.0 g of phosphorus are usual with each dialysis, the addition of these losses to those in stool and urine will effectively cancel the positive phosphorus balances shown in Table 2. Nevertheless they still permit deductions to be drawn from the changes in fecal data presented. The decrease in fecal calcium during DHT could have been due either to augmented absorption or to a decrease in endogenous secreted calcium or a combination of both. We have previously reported endogenous calcium to be normal in patients with chronic uremia, * but this has recently been questioned.6 Because of possible differences in patient populations this was reexamined and found to be unchanged, supporting the view that the decrease in fecal calcium with DHT is due to a true increase in absorption. The balance data support our previous observations that calcium absorption is impaired in chronic renal failure but that with a calcium intake of 0.8 g or more daily, balance is usually close to equilibrium.4*7 The failure to adapt to a low calcium intake is presumably due to the abnormalities in vitamin D metabolism leading to a deficiency of calcium-binding protein in the intestinal cells.8 That this block can be overcome or at least minimized by increasing the luminal calcium concentration suggests that absorption of calcium at high levels of intake may be partially independent of the vitamin D-sensitive transport process. The improvement in calcium balance produced by DHT provides an explanation for the healing of renal osteodystrophy observed previouslv in dialysis patients treated with this agent. Equivalent doses of calciferol had no effect on *‘Ca absorption and would not be expected to augment stable calcium absorption to the extent seen with DHT.3 It has been suggested in view of the identification of 1,25-dihydroxycholecalciferol as the hormone acting on the
824
KAYE AND SAGAR
intestine, that hydroxylation at carbon 1 will be impaired in the presence of severe renal failure as this process occurs uniquely in the kidney.g DHT is, however, alreadv hydroxylated at the steric equivalent of Cl and onlv requires preliminary hydroxylation at c25 by the liver. This may explain the difference in potency between DHT and calciferol in augmenting calcium absorption in patients with chronic uremia. It was apparent that calcium absorption was better both before and after DHT in the dialyzed Group II patients than those with more residual renal function. This would seem difficult to reconcile with the requirement of having some functioning renal tissue for hydroxylation of 25-hvdroxycholecalciferol as the reverse findings would have been expected. The data lead one to SUSpect that some additional process not directly vitamin D-dependent may be affected bv “uremia” itself. This could be a nonspecific depression of general protein svnthesis, which is alleviated by dialysis but leaves unchanged the specific block in vitamin D metabolism. Doses of DHT between 0.25 and 0.375 mg should be adequate for correction of the defect in calcium absorption in dialyzed patients with uremia. It is apnarent from the balance data that this dosage will be inadequate for most nondialvzed patients with chronic uremia. ACKNOWLEDGMENT Miss S. McDonagh, research dietitian, supervised all studies. Miss M. Hellstrom, Mrs. J. Henderson, and Miss M. White gave valuable technical assistance, and Miss A. Thompson. R.N., helped with the dialysis patients. Finally, we wish to thank the patients who voJunteered for the study and Miss D. Thornber for secretarial assistance.
REFERENCES 1. Harrison, H. E., Lifshitz, F., and Blizzard, R. M.: Comparison between crystalline dihydrotachysterol and calciferol in patients requiring pharmacologic vitamin D therapy. New Eng. J. Med. 276 :894, 1967. 2. Kaye, M., Just, G., and Wilson, M.: Comparison of dihydrotachysterol, hytakerol and calciferol. Canad. J. l’hysiol. Pharmacol. 49 :857,1971. 3. Kaye, M., Chatterjee, G., Cohen, G. F., and Sagar, S.: Arrest of hyperparathyroid bone disease with dihydrotachysterol in pachronic hemodialysis. tients undergoing Ann. Intern. Med. 73:225, 1970. 4. Kaye, M., and Silverman, M.: Calcium metabolism in chronic renal failure. J. Lab. Clin. Med. 66:535, 1965. 5. Kaye, M., Mangel, R., and Neubauer, E.: Studies in calcium metabolism in patients on chronic hemodialysis. In Proceedings, Third Conference of the European
Dialysis and Transplant Association, 1961, p. 17. 6. Reiner, M., Nadarazah, A., Woolhouse, N. J. Y., Nunziata, V., Sevitt, L., and Joplin, G. F.: Calcium absorption and excretion in the gut in chronic renal failure. Israel J. Med. Sci. 7:522, 1971. 7. Kaye, M., Pritchard, J. E., Halpenny, G. W., and Light, W.: Bone disease in chronic renal failure with particular reference to osteosclerosis. Medicine 39:X7, 1960. 8. Avioli, L. V., Scott, S., Lee, S. W., and DeLuca, H. F.: Intestinal calcium absorption: Nature of defect in chronic renal disease. Science 166 :1154, 1969. 9. Fraser, D. R., and Kodicek, E.: Unique biosynthesis by kidney of a biologically active vitamin D metabolite. Nature (London) 228 ~764, 1970.
Kaye and S. Sagar
The effect of dihydrotachysterol on gastrointestinal absorption of calcium was studied in five undialyzed and five dialyzed patients with chronic uremia. Fecal calcium decreased and calcium
balance of the changes dialyzed
became less negative in nine ten patients; however, the were more marked in the patients.
A
S PREVIOUSLY SHOWN, dihydrotachysterolz (DHT), a compound very similar to vitamin DZ or calciferol chemically, has nonetheless different was noted the favorable rebiologic properties. I>2 Among these differences sponse of long-term dialysis patients with active secondary hyperparathyroidism due to chronic renal failure treated with this agent, whereas a similar dose of calciferol appeared ineffective. In the present study the external calcium balance was assessed in patients with chronic renal failure before and after administration of dihydrotachysterol. Those being treated by dialysis showed a considerably greater decrease in fecal calcium and a more positive calcium balance after DHT than the nondialyzed patients. MATERIALS
AND METHODS
Two groups of patients were studied. In those with residual renal function, Group I, there were five patients, and a total of seven studies were carried out. In Group II there were five patients stabilized on a chronic dialysis program. A single study was conducted on each patient. Collections of stool and urine were carried out in a metabolic unit supervised by a research dietitian and technician. Each patient received a diet as identical in calcium content and general nature as possible to that which the patient was consuming before admission. Two diets were employed and given on alternate days. These were prepared before the start of the study and a day’s diet of each was analyzed. Any medications being taken by the patients such as supplemental calcium or phosphate binders, are indicated in Table 1. These were continued in the same dosage as were the hemodialysis schedules. Kiil dialyzers were used with a dialyzate calcium of 6 mg/loo ml and no phosphate. None of the patients had received pharmacologic doses of vitamin D, but the patients on dialysis took a multivitamin tablet containing 400 units of Dz. In the three cases where DHT had previously been used, 5, 6, and 2 mo had elapsed, since it was discontinued until the beginning of the study. Chromic oxide was used as a fecal marker, 0.25 g 3 times daily with meals; all‘calculations for daily fecal excretion were based on this. Stool and urine were collected in individual pools and the duration of each pool and results obtained before and after DHT administration are shown in Tables 2-6. The equilibration period and the
From the Division of Nephrology, Department of Medicine, the Montrenl General Hospital, Montreal, Quebec, Canada. Received for publication November 29, 1971. Supported by USPHS Grant I”843-66-542 and Medical Research Council Grant MA-3224 for the Metabolic Unit. Michael Kaye, M.B., F.R.C.P. (C): Director, Division of Nephrology, Department of Medicine, the Montreal General Hospital; and Associate Professor, Department of Medicine, McGill University, Montreal, Quebec, Canada. S. Sagar, M.B., B.S.: Clinical Fellow in Nephrology, Department of Medicine, the Montreal General Hospital, Montrenl, Quebec, Canada, 7uly 7969-Tune 1971. Metabolism,
Vol. 21, No. 9 (September),
1972
815
I I I I
I II
II II II
II
MUL I MUL II CAN McM BAR I BAR II ROY GEN
DIS NAN PIT
LAW
34
49 35 53
65 66 76 72 46 46 59 26
Age
l
As calcium gluconogalactogfuconate t As calcium carbonate. * AS calcium gluconate.
I
I
Group
__
Name
_~_
(Sandor).
Chronic glomerulonephritis
Chronic glomerulonephritis Chronic glomerulonephritis Nephrosclerosis
Chronic pyelonephritis Chronic pyelonephritis Chronic pyelonephritis Polycystic disease Nephrosclerosis Nephrosclerosis Chronic glomerulonephritis Heretitary nephritis
Diagnosis
4.3
7.2 5.6 4.1
71.4 9.7 9.6 9.6
5.0 6.9 6.2 4.6 6.6 7.6 6.1 5.4
P mg/lOo ml
7.5 6.1 10.2 9.0 9.2 6.3 7.6 9.3
Ca mg/lOO ml
Serum
Table 1. Clinical Data on Patients
0.3
0.9 0 1.5
30
30 36 28
30
Clearance ml/min
4.1 3.4 2.7 22.4 7.2 6.1 2.6 0.9
Hours Dialysis, Weekly
Creatinine
176* mg Ca/day orally 660’ mg Ca/day orally Aluminum hydroxide 2 tabs/day 680’ mg Ca/day orally
1.Ot g Ca/day orally -
660’ mg Ca/day orally -
Medication
I
I
Mean
Mean
Mean
Mean
Mean
‘Percent
ROY
Mean BARII
BAR
McM
CAN
Mean MULII
MUL
Name
1 2
1 2
1 2
1 2
1 2
1319
530 1316 1322
435 1035 1098 1067 639 639 639 525 534
1028 1028 1028 379 377 378 378 435 434
1 2
1 2 3
take mwday
Pariod
dose absorbed.
6 8
7 6
6 7
7 6
7
7 7
No. Days
In-
Ca
1293
703 1217 1369
528 895 951 923 657 617 637 705 700
1000 1035 1018 564 595 612 590 538 518
Ca Stool mwday
Control
18
41 23 13
86 31 34 32 33 57 45 41 41
19 28 24 16 30 24 23 70 101
Ca Urine mwday
9
+8
+ -
76 60
-214
-179 +109 +113 +112 - 51 - 35 - 43 -221 -207
+
- 35 - 14 -201 -248 -258 -235 -173 -185
Balante mglday
65
45 61 69
68 52 34 43 58 53 56 47 43
38 29 34 59 63 43 55 56 79
Ca47*
4 3 5
7 7 7
7 7
7 7
4 7 4
7 6
7 7
NO. Days
4 5 6
4 5 6
4 5
4 5
4 5 6
5 6
4 5
Period
0.25 0.25 0.25
0.5 0.5 0.5
0.25 0.25
0.25 0.25
0.25 0.25 0.25
0.25 0.25
0.25 0.25
DHT mg/day
1323
351 1333 1322 1314
435 1011 1043 1027 639 639 639 525 204 325
379 435 434 435
1028 1028 1028 379 378
Ca Intake mwday
Table 2. Calcium Balance--Group
I
1184
574 1165 1170 1216
373 898 793 846 658 672 665 686 577 458
532 429 353 337
972 1007 990 519 545
Ca stool mwday
24
45 27 21 24
86 25 28 27 57 14 36 50 41 45
25 88 86 86
19 13 16 22 28
Ca Urine w/day
24
12
+115
70
73 +
74
51 67 -
97 42 37 40 25 32 29 40 47 68
54 94 100 -
50 51 51 50 57
Ca4”
-268 $141 +131
-t-68 j-222 j-154 - 76 - 47 - 62 -211 -414 -178
-
+
-178 - 80 -5
+ 37 +6 + 19 -162 -195
Balante mwday
DHT
57
33
54
19
42
+107
-
-
+
-j-l55
+
+
ABalante mgfday
$5
-l-6
-27
-3
+29
-1
+17
A Ca47’
LAW
PIT
NAN
DIS
GEN
7 7 7
7 7
7 7
7 7
10 7
1 2 3
1 2
1 2
1 2
1 2
Period
426 426 426 490 470 480 1095 1101 1098 876 879 878 1200 1200 1199 1200
lPercentdoseabsorbed.
Mean
Mean
Mean
Mean
Mean
Name
No. Days
Ca Intake mglday
481 510 475 493 1010 890 950 542 508 525 1332 1338 1127 1266
474 487
Ca stool mg/day
Control
3 2
3 2 3 1 3
-
17 17 17 26 17 22
w/day
Ca Urine
+ -
69 68
+148 +331 +369 +350 -133 -141
+ 85 +211
- 65 - 78 - 72 -46 - 22 - 35
w/day
Balante
65 46 56 62 39 50 46 55 50 46 52 49 12 63 62 46
Ca47’
7 6
7 8
7 7
7 12
10 10
No. Days
5 6
4 5
4 5
4 5
4 5
Period
0.25 0.25
0.25 0.25
0.375 0.375
0.25 0.25
0.25 0.25
DHT mgldw
Table 3.Calcium Balance-Group
1170
426 426 426 486 451 469 1095 1101 1098 879 878 879 1200 1140
Ca Intake mg/day
II
1041
896 879 888 481 464 473 1069 1013
434 371 403 323 121 222
Ca Stool mgfday
6
2 3 3 7 4
16 22 19 13 11 12
Ca Urine mg/day
+123
- 24 + 33 + 4 +150 +319 +235 4199 +222 +210 f396 +411 +403 +124 +I23
Balante mg/day
DHT
55
81 82 82 88 89 89 83 76 80 47 46 47 65 44
Ca47’
76
53
62
+191
+
+
+270
+
ABalante mglday
A
-kg
-2
+30
+39
+26
Ca47’
9 W
I
I
Mean
Mean
Mean
Mean
Mean
7 6
7 7
6 6
7 6
6 7
7 7 6
1 2
2
1
1 2
1 2
1 2
1 2 3
1 2
7 7
411
367
662 375 359
291 469 473 471 259 218 239 720 603
745 1074 1074 1074 690 690 690 659 869
664 402 419
298 314 306 361 354 365 360 292 290
-
P Stool mglday
160
487 170 150
401 529 575 552 517 532 525 474 499
180 260 230 257 342 315 305 440 361
P Urine mglday
Control
622 610 616 587 577 582 582 745 744
'Per cent dose absorbed.
ROY
Mean BAR II
BAR
McM
CANI
Mean MULII
MUL
Name
Period
No. Days
P Intake mg/day
13 93
-116
-285 -143 - 90
+ 53 + 76 + 26 + 51 - 86 - 60 - 74 -335 -233
+ +
+ 16 + 60 - 31 -119 - 98 - 83
+144
Balante mglday
65
45 61 69
68 52 34 43 58 53 56 47 43
38 29 34 59 63 43 55 56 79
Ca47’
4 3 5
7 7 7
7 7
7 7
4 7 4
7 6
7 7
No. Days
4 5 6
4 5 6
4 5
4 5
4 5 6
5 6
4 5
Period
Table4.Phosphorus
0.25 0.25 0.25
0.5 0.5 0.5
0.25 0.25
0.25 0.25
0.25 0.25 0.25
0.25 0.25
0.25 0.25
DHT mg/day
585 745 744 745 745 1080 1060 1080 691 689 690 859 401 517 592 447 419 398 421
622 610 616 587 582
P Intake mg/day
Balance-Group i
347 248 255 337 260 428 369 399 207 169 198 584 518 471 524 393 391 366 383
516 510 513 354 339
P Stool mg/day
352 362 560 560 501 524 592 556 589 661 615 535 490 450 492 120 110 130 120
220 355 288 309 395
P Urine mgjday
-114 +115 - 71 -152 - 36 +128 +119 +123 - 85 -161 -123 -260 -807 -404 424 - 66 -62 - 98 - 82
-114 -255 -185 - 76 -152
Balante mgjday
DHT
54 94 100 97 42 37 40 25 32 29 40 47 66 51 67 73 70
50 51 51 50 57
Ca47’
31
49
72
+
34
-139
-
+
-104
-
-265
AEialante mglday
A
i-5
i-6
-27
-3
f29
-1
f17
Ca47’
Mean
Mean
Mean
Mean
Mean
7 7 7
7 7
7 7
7 7
10 7
1 2 3
1 2
1 2
1 2
1 2
Period
667 693 690 565 534 550 771 759 765 654 640 a47 ii08 1112 1106 1109
511 324 418 278 236 257 1651 1286 1469 584 620 602 406 392 372 390
mglday
P
Stool
take
mglday
lPercentdoseabsorbed.
LAW
PIT
NAN
DIS
GEN
Name
No. Days
Control
P In-
55 47 51 2 14 30 15
29 28 29 45 31 38 -
P Urine mgfday
1-243 $242 +267 $255 -680 -527 -704 +215 +173 +194 +700 +706 4706 +704
f147 +341
Balante mgldaY
65 46 56 62 39 50 45 55 50 46 52 49 12 63 62 46
Ca47*
7 6
7 a
7 7
7 12
10 10
No. Days
II
354
0.25 0.25
0.25 0.25
771 759 765 a40 a48 a44 1108 1020 1064
5 6
4 5
4 5
0.375 0.375
563 464 514
0.25 0.25
4 5
276 254 265 212 155 la4 1241 1491 1366 605 594 600 320 388 687 687 687
0.25 0.25
4 5
P Stool mgldey
DHT mg/daY
Period
P Intake mg/day
Table 5. Phosphorus Balance-Group
26
27 45 36 26 21 23 33 18 26 38 14
P Urine
$684
+364 +3aa +386 +325 +2a6 $307 470 -732 -601 +202 +236 +216 +750 +618
Balante mg/day
DHT
55
al a2 62 aa a9 a9 a3 76 80 47 46 47 65 44
Ca47*
52
-
+
20
24
f103
+
+143
%VW
ABalante
*A
+9
-2
+30
$39
$26
Ca47’
x
15
16 16
792 752
712
771 816 794
l
627 506
365
613 743 776
33 207
380
36 11 25
Urine w/day
or per cent
Stool w/day
balance
Intake w/day
Per cent dose absorbed. TA is the net change in either
Group
I
15 16 16
Group II Groups I and II
Group I Group II Groups I and II Phosphorus
Calcium
NO. Days
Control
53
60 62 9
radioactive
+I32 $ 39
-
+ -
Balante w/day
Table 6. Mean Values
calcium
50 51
52
52 50 51
Ca47’
775 726
676
740 608 774
Intake m/day
554 466
376
736 605 672
stool w/day
and Phosphorus
absorption.
16 16
15
15 16 16
No. Days
for Calcium
28 223
416
37 10 24
Urine w/day
Balance
35 +193 + 78
Balance w/day
j-193 + 37
-120
DHT
71 64
56
56 71 64
Ca47’
-I- 61 2
-67
-t-45 +131 + 67
ABalance w/day
$21 fl3
$4
i-4 +21 $13
Ca47’
A
5
z
it
C
2
E
E
F i;
822
KAYE AND SAGAR
first pool after DHT administration
of 4-5 days duration have been excluded. Radioactive calcium absorption was measured by giving orally 10 /Ki 47Ca at 8:00 a.m. after overnight fasting. The solution did not contain carrier calcium but two so-ml washes with tap water containing 4 mg/IOO ml calcium were taken to rinse the container. Stools were collected as part of the balance for the following 7 days, and homogenized and weighed aliquots were counted in duplicate together with a suitably diluted standard of the administered 47Ca. The 47Sc counts were excluded by appropriate window settings. Clinical data on the subjects are shown in Table I. Analytical methods were similar to those described previ0usly.334The DHT used was kindly supplied by Dr. C. W. Birkett of Winthrop Laboratories as Hytakerol. This has been shown to be chemically and biologically similar to pure crystalline DHT.2 Several months after completing the balance study and stopping DHT, all subjects in Group II, three other long-term dialysis patients, and one patient with chronic uremia awaiting transplantation were given 47Ca intravenously. The excretion of the isotope in the stool was determined over the following 5 days.
RESULTS
Control
Period
The findings are shown in Tables 2 and 3 for calcium and Tables 4 and s for phosphorus, and summarized in Table 6. The mean calcium intake was similar in the two groups, being 771 mg/day for Group I and 816 mg/day for Group II. Urine calcium was slightly higher in those not yet being dialyzed as would be expected. In Group II, the calcium balance was slightly positive and slightly negative in Group I, +62 mg/day as compared with -80 mg/day. The difference could be mainly accounted for by the smaller fecal calcium in Group II. Radioactive calcium absorption was comparable and low in both groups. If the two groups were pooled and divided into those with calcium intakes above and below 800 mg/day, the balance was $-89 mg/day where the intake was in excess of 800 mg daily and -129 mg/day when it was below. Phosphorus intake in the two groups was similar in the control period. The mean balance was -53 mglday for Group I and +I32 mglday for Group II. The difference is due to the negligible urinary phosphorus loss in this group. As the losses by hemodialysis have not been allowed for, overall balance would be actually much less positive for Group II. DHT Period Calcium intake was similar to the control period; however, balance was now positive in all the Group II patients and negative in three of the Group I patients. When the change in calcium balance was calculated, ACa in Table 2, all balances became more positive with the exception of the two studies done on BAR. This change in balance was due to a mean decrease in fecal calcium of 138 mg/day in Group II and 75 mg/dav in Group I. The improvement in calcium balance after DHT in the nondialyzed patients is small and variable from patient to patient. This contrasts with the uniform and in some instances quite striking positive balance seen in the Group II dialvzed patients. If the two groups are pooled, the overall change in calcium balance was significant using the Wilcoxon rank test, p
unchanged
in Group
in Group II and was I. The pooled change was almost zero. The change in
CALCIUM
ABSORPTION
823
IN UREMIA
phosphorus balance in Group II was less than the change in calcium balance and the molar ratio nCa/nP was 1.66, which is similar to the Call’ ratio of hydroxyapatite. The 47Ca absorption followed the change in stable calcium absorption and comparison of n*sCa and A4’Ca gave a correlation coefficient r = 0.6547, p <0.05. *‘Ca intravenously The nine subjects excreted 7.8 F 1.2 per cent of the administered dose, range 4.7%-16.4%, in the stool over the subsequent 5 days. This is similar to our previous values of 7.2% for normal subjects and 8.1% for patients with uremia with a calculated endogenous fecal calcium of 2.3 and 2.6 mg/ kg/day for control patients and patients with uremia, respectively.5 DISCUSSION
It should be noted that the balance data reported for the dialyzed patients do not represent the total gains or losses because no account has been taken of the changes occuring during hemodialysis. However, with a dialyzate calcium of 6 mg/loo ml the net transfer of calcium across the dialyzer membrane is minimal if the plasma calcium is in the normal range.s As we were mainly interested in intestinal absorption, it was felt to be permissible to ignore the changes during dialysis. In the case of phosphorus as the dialyzate is phosphate free and losses of 0.5-1.0 g of phosphorus are usual with each dialysis, the addition of these losses to those in stool and urine will effectively cancel the positive phosphorus balances shown in Table 2. Nevertheless they still permit deductions to be drawn from the changes in fecal data presented. The decrease in fecal calcium during DHT could have been due either to augmented absorption or to a decrease in endogenous secreted calcium or a combination of both. We have previously reported endogenous calcium to be normal in patients with chronic uremia, * but this has recently been questioned.6 Because of possible differences in patient populations this was reexamined and found to be unchanged, supporting the view that the decrease in fecal calcium with DHT is due to a true increase in absorption. The balance data support our previous observations that calcium absorption is impaired in chronic renal failure but that with a calcium intake of 0.8 g or more daily, balance is usually close to equilibrium.4*7 The failure to adapt to a low calcium intake is presumably due to the abnormalities in vitamin D metabolism leading to a deficiency of calcium-binding protein in the intestinal cells.8 That this block can be overcome or at least minimized by increasing the luminal calcium concentration suggests that absorption of calcium at high levels of intake may be partially independent of the vitamin D-sensitive transport process. The improvement in calcium balance produced by DHT provides an explanation for the healing of renal osteodystrophy observed previouslv in dialysis patients treated with this agent. Equivalent doses of calciferol had no effect on *‘Ca absorption and would not be expected to augment stable calcium absorption to the extent seen with DHT.3 It has been suggested in view of the identification of 1,25-dihydroxycholecalciferol as the hormone acting on the
824
KAYE AND SAGAR
intestine, that hydroxylation at carbon 1 will be impaired in the presence of severe renal failure as this process occurs uniquely in the kidney.g DHT is, however, alreadv hydroxylated at the steric equivalent of Cl and onlv requires preliminary hydroxylation at c25 by the liver. This may explain the difference in potency between DHT and calciferol in augmenting calcium absorption in patients with chronic uremia. It was apparent that calcium absorption was better both before and after DHT in the dialyzed Group II patients than those with more residual renal function. This would seem difficult to reconcile with the requirement of having some functioning renal tissue for hydroxylation of 25-hvdroxycholecalciferol as the reverse findings would have been expected. The data lead one to SUSpect that some additional process not directly vitamin D-dependent may be affected bv “uremia” itself. This could be a nonspecific depression of general protein svnthesis, which is alleviated by dialysis but leaves unchanged the specific block in vitamin D metabolism. Doses of DHT between 0.25 and 0.375 mg should be adequate for correction of the defect in calcium absorption in dialyzed patients with uremia. It is apnarent from the balance data that this dosage will be inadequate for most nondialvzed patients with chronic uremia. ACKNOWLEDGMENT Miss S. McDonagh, research dietitian, supervised all studies. Miss M. Hellstrom, Mrs. J. Henderson, and Miss M. White gave valuable technical assistance, and Miss A. Thompson. R.N., helped with the dialysis patients. Finally, we wish to thank the patients who voJunteered for the study and Miss D. Thornber for secretarial assistance.
REFERENCES 1. Harrison, H. E., Lifshitz, F., and Blizzard, R. M.: Comparison between crystalline dihydrotachysterol and calciferol in patients requiring pharmacologic vitamin D therapy. New Eng. J. Med. 276 :894, 1967. 2. Kaye, M., Just, G., and Wilson, M.: Comparison of dihydrotachysterol, hytakerol and calciferol. Canad. J. l’hysiol. Pharmacol. 49 :857,1971. 3. Kaye, M., Chatterjee, G., Cohen, G. F., and Sagar, S.: Arrest of hyperparathyroid bone disease with dihydrotachysterol in pachronic hemodialysis. tients undergoing Ann. Intern. Med. 73:225, 1970. 4. Kaye, M., and Silverman, M.: Calcium metabolism in chronic renal failure. J. Lab. Clin. Med. 66:535, 1965. 5. Kaye, M., Mangel, R., and Neubauer, E.: Studies in calcium metabolism in patients on chronic hemodialysis. In Proceedings, Third Conference of the European
Dialysis and Transplant Association, 1961, p. 17. 6. Reiner, M., Nadarazah, A., Woolhouse, N. J. Y., Nunziata, V., Sevitt, L., and Joplin, G. F.: Calcium absorption and excretion in the gut in chronic renal failure. Israel J. Med. Sci. 7:522, 1971. 7. Kaye, M., Pritchard, J. E., Halpenny, G. W., and Light, W.: Bone disease in chronic renal failure with particular reference to osteosclerosis. Medicine 39:X7, 1960. 8. Avioli, L. V., Scott, S., Lee, S. W., and DeLuca, H. F.: Intestinal calcium absorption: Nature of defect in chronic renal disease. Science 166 :1154, 1969. 9. Fraser, D. R., and Kodicek, E.: Unique biosynthesis by kidney of a biologically active vitamin D metabolite. Nature (London) 228 ~764, 1970.