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Metabolic studies of [75Se]selenocystine and [75Se]selenomethionine in the rat

Published online by Cambridge University Press:  09 March 2007

Christine D. Thomson
Affiliation:
Department of Nutrition and Department of Medicine, University of Otago, Dunedin, New Zealand
Bridget A. Robinson
Affiliation:
Department of Nutrition and Department of Medicine, University of Otago, Dunedin, New Zealand
R. D. H. Stewart
Affiliation:
Department of Nutrition and Department of Medicine, University of Otago, Dunedin, New Zealand
Marion F. Robinson
Affiliation:
Department of Nutrition and Department of Medicine, University of Otago, Dunedin, New Zealand
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Abstract

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1. The long-term fate in rats of an oral dose of [75Se]selenocystine was compared with that of an oral dose of [75Se]selenomethionine.

2. Urinary and faecal radioactivities were measured during the 1st week and whole-body radioactivity was determined for 10 weeks. Rats were killed at weekly intervals for 4 weeks and at weeks 6 and 10 for analysis of tissue distribution of 75Se.

3. Intestinal absorption of [75Se]selenocystine was 81% of the administered dose; that of [75Se]selenomethionine was 86%. Urinary excretion of absorbed [75Se]selenocystine was 13.9% and that of [75Se]selenomethionine was 5.8%, in the 1st week.

4. Whole-body retention of 75Se was greater for [75Se]selenomethionine than for [75Se]-selenocystine but after the 1st week it decreased at a similar rate in both groups. Tissue distribution of retained 75Se was also similar in both groups.

5. The initial utilization of [75Se]selenocystine was different from that of [75Se]selenomethionine. However, after the 1st week 75Se from both sources appeared to be metabolized similarly, suggesting that dietary Se of both forms is ultimately incorporated into the same metabolic pool.

6. When these findings were compared with those of earlier studies with [75Se]selenite and 75Se incorporated in vivo into rabbit kidney (RK-75Se) (Thomson, Stewart & Robinson, 1975) the metabolism of [75Se]selenocystine resembled that of [75Se]selenite and RK-75Se, rather than that of [75Se]selenomethionine.

Type
Papers of direct relevance to Clinical and Human Nutrition
Copyright
Copyright © The Nutrition Society 1975

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