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Intestinal absorption of α-tocopherol
Life Sciences No . 4, pp . 115-117, 1962 . Great Britain .
Pergamon Press Ltd .
Printed in
INTESTINAL ABSORPTION OF a-TOCOPI~ROL P . Johnson and W.F .R . Pover Department of Medical Biochemistry and Pharmacology University of Birmingham (Received 28 February 1962)
DURING a study of the intestinal absorption of lipid-soluble substances an investigation was carried out into the .pathway of absorption of l~-labelled a-tocopherol .
Although a large volume of information appears in the literature
concerning most other aspects of the tocopherols, information concerning their fate in the animal body is fragmentary.
The factor of intestinal absorption has
received little attention, apart from one or two indirect investigations by means of tolerance tests based on plasma tocopherol curves, bioassays of total body tissue .4 and shown to be unsatisfactory .
l-3
or by means of
These methods have been subsequently criticised Swick and Baumanns found that absorption of
a-tocopherol is relatively fast, but no information has appeared in the literature concerning the pathway of absorption .
Demonstration of the presence of
a-tocopherol in lymph following oral feeding would indicate the route of absorption . Administration of radioactive a-tocopherol and its esters in oil solution to rats has normally resulted in high faecal excretion of radioactivity . 6
A
general criticism of previous work is that the so-called trace doses of 10-15 mg used in the experiments are in our opinion massive doses .
These doses may have
been necessary to allow subsequent analyses if low specific activity carbonlabelling or inefficient counting techniques were employed . In the present work, 1~-a-tocopherol was labelled in the methyl substituents at positions 5 and 7, by direct methylation of 8-tocopherol .*
The resulting
Adapted from a method of Dr . J . Green (Vitamins Ltd ., England) kindly supplied in a private com~nication .
116
INTESTINAL ABSORPTION OF a-TOCOPI~ROL
No .4
high specific activity (1 me/mM) a-tocopherol was fed in 60 pg quantities as a single dose in 0 .5 ml olive oil, to rats with cannulated intestinal lymphatic ducts .
The resulting chyle was collected over a period of days or until flow
ceased, using an internal collection reservoir after the method of Tasker~ . The chyle lipids were analysed for radioactivity by liquid scintillation counting .
The results (Table 1) show that incorporation of radioactivity into
the chyle lipids occurs to an appreciable extent .
Preliminary two-dimensional
chromatography indicates that a-tocopherol passes unchanged into the lymphatic system . TABLE 1
Allowing for loss of chyle due to the operative technique and overflow of the collection reservoir during overnight periods, it is evident that absorption of a-tocopherol by the lymphatic route is probably greater than indicated by the present results .
A direct comparison with absorption of trace quantities of
labelled palmitic acid, which is known to be well-absorbed via the lymphatic system, suggests that a-tocopherol is absorbed to the extent of 10 per cent of the administered dose . g
Previous reports on the low incidence of tocopherol in
urine were confirmed in the present work (Table 2), although the detection of some urinary radioactivity indicates that a water-soluble metabolite cannot be excluded .
In view of the well-known high faecal recoveries of a-tocopherol
after feeding, the results suggest that the primary absorption pathway of
No .4
INTESTINAL ABSORPTION OF a-TOCOPF~ROL
a-tocopherol is via the intestinal lacteals into the chyle .
Further details of
the work will be published in the near future . TABLE 2
Animal no .
Radioactivity recovered from urine after 8 days
Recovered radioactivity as percentage of dose feä
d~s 6
ll .g
0 .37
7
3 .0
0 .09
8
10 .6
0 .33
9
6 .7
o .zo
Acknowledgements - The authors wish to acknowledge the award of a University of Birmingham Research Scholarship to one of us (P . Johnson) . We also thank Miss J. Kight for valuable technical assistance and Professor A .C . Frazer for his interest . Referencès A .E . SOBEL, A . R06ENBERG, R . GEWLDIG, E . ENG~EL, M . 1NEST and H . (CRAMER, Fed . Proc . $, 253 (1949) . 2.
G . KLATSKIN and W.A . KR~EFII., ,~ . Clin . Invest . ~Q, 1528 (1950) .
3.
E . POPPER, A . DUBIN, F . STEIGMANN and F .P . 1~SSER, J . Lab . Clin . Med . 34, 648 (1949) .
4.
K.E . MASON, J. Nutrition 23, 71 (1942) "
5.
R .W . SWICK and C .A . BAUMANN, Arch . Biochem . Bioohvs . ~, 120 (1952) .
6.
E .J . SIMON, C .A . GROSS and A .T . MILI~RAT, J. Biol . Chem . ,~.1, 797 (1956) .
7.
R .R . TASKFR, J. Phvsiol . ~, 292 (1951)
8.
P . JOI~WSW and W.F .R . DOVER, Vth International Congress of Biochemistrv, Moscow 1961, Section 12 .
Pergamon Press Ltd .
Printed in
INTESTINAL ABSORPTION OF a-TOCOPI~ROL P . Johnson and W.F .R . Pover Department of Medical Biochemistry and Pharmacology University of Birmingham (Received 28 February 1962)
DURING a study of the intestinal absorption of lipid-soluble substances an investigation was carried out into the .pathway of absorption of l~-labelled a-tocopherol .
Although a large volume of information appears in the literature
concerning most other aspects of the tocopherols, information concerning their fate in the animal body is fragmentary.
The factor of intestinal absorption has
received little attention, apart from one or two indirect investigations by means of tolerance tests based on plasma tocopherol curves, bioassays of total body tissue .4 and shown to be unsatisfactory .
l-3
or by means of
These methods have been subsequently criticised Swick and Baumanns found that absorption of
a-tocopherol is relatively fast, but no information has appeared in the literature concerning the pathway of absorption .
Demonstration of the presence of
a-tocopherol in lymph following oral feeding would indicate the route of absorption . Administration of radioactive a-tocopherol and its esters in oil solution to rats has normally resulted in high faecal excretion of radioactivity . 6
A
general criticism of previous work is that the so-called trace doses of 10-15 mg used in the experiments are in our opinion massive doses .
These doses may have
been necessary to allow subsequent analyses if low specific activity carbonlabelling or inefficient counting techniques were employed . In the present work, 1~-a-tocopherol was labelled in the methyl substituents at positions 5 and 7, by direct methylation of 8-tocopherol .*
The resulting
Adapted from a method of Dr . J . Green (Vitamins Ltd ., England) kindly supplied in a private com~nication .
116
INTESTINAL ABSORPTION OF a-TOCOPI~ROL
No .4
high specific activity (1 me/mM) a-tocopherol was fed in 60 pg quantities as a single dose in 0 .5 ml olive oil, to rats with cannulated intestinal lymphatic ducts .
The resulting chyle was collected over a period of days or until flow
ceased, using an internal collection reservoir after the method of Tasker~ . The chyle lipids were analysed for radioactivity by liquid scintillation counting .
The results (Table 1) show that incorporation of radioactivity into
the chyle lipids occurs to an appreciable extent .
Preliminary two-dimensional
chromatography indicates that a-tocopherol passes unchanged into the lymphatic system . TABLE 1
Allowing for loss of chyle due to the operative technique and overflow of the collection reservoir during overnight periods, it is evident that absorption of a-tocopherol by the lymphatic route is probably greater than indicated by the present results .
A direct comparison with absorption of trace quantities of
labelled palmitic acid, which is known to be well-absorbed via the lymphatic system, suggests that a-tocopherol is absorbed to the extent of 10 per cent of the administered dose . g
Previous reports on the low incidence of tocopherol in
urine were confirmed in the present work (Table 2), although the detection of some urinary radioactivity indicates that a water-soluble metabolite cannot be excluded .
In view of the well-known high faecal recoveries of a-tocopherol
after feeding, the results suggest that the primary absorption pathway of
No .4
INTESTINAL ABSORPTION OF a-TOCOPF~ROL
a-tocopherol is via the intestinal lacteals into the chyle .
Further details of
the work will be published in the near future . TABLE 2
Animal no .
Radioactivity recovered from urine after 8 days
Recovered radioactivity as percentage of dose feä
d~s 6
ll .g
0 .37
7
3 .0
0 .09
8
10 .6
0 .33
9
6 .7
o .zo
Acknowledgements - The authors wish to acknowledge the award of a University of Birmingham Research Scholarship to one of us (P . Johnson) . We also thank Miss J. Kight for valuable technical assistance and Professor A .C . Frazer for his interest . Referencès A .E . SOBEL, A . R06ENBERG, R . GEWLDIG, E . ENG~EL, M . 1NEST and H . (CRAMER, Fed . Proc . $, 253 (1949) . 2.
G . KLATSKIN and W.A . KR~EFII., ,~ . Clin . Invest . ~Q, 1528 (1950) .
3.
E . POPPER, A . DUBIN, F . STEIGMANN and F .P . 1~SSER, J . Lab . Clin . Med . 34, 648 (1949) .
4.
K.E . MASON, J. Nutrition 23, 71 (1942) "
5.
R .W . SWICK and C .A . BAUMANN, Arch . Biochem . Bioohvs . ~, 120 (1952) .
6.
E .J . SIMON, C .A . GROSS and A .T . MILI~RAT, J. Biol . Chem . ,~.1, 797 (1956) .
7.
R .R . TASKFR, J. Phvsiol . ~, 292 (1951)
8.
P . JOI~WSW and W.F .R . DOVER, Vth International Congress of Biochemistrv, Moscow 1961, Section 12 .