Biotransformations of 25-hydroxyvitamin D3 by kidney microsomes. |
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Authors: | R W Gray A E Caldas J L Weber J G Ghazarian |
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Affiliation: | 1. Department of Biochemistry Medical College of Wisconsin Milwaukee, Wisconsin 53233 USA;2. Department of Medicine Medical College of Wisconsin Milwaukee, Wisconsin 53233 USA |
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Abstract: | Vitamin D3-deficient chick kidney microsomes metabolize 25-hydroxy-[26(27)-methyl-3H]-vitamin D3 to yet structurally unidentified polar metabolites previously designated MIC-I and MIC-II. Kidney microsomes of vitamin D3-repleted chicks could not be demonstrated to produce these metabolites when 3H was the radioactive isotope in positions C-26 and C-27 of the substrate. However, when 25-hydroxy-[26,27-14C]-vitamin D3 was the radioactive substrate, MIC-I and MIC-II production was independent of the vitamin D3 status of the chicks. These results suggest that under conditions of vitamin D3-sufficiency, there is augmented sequential kidney metabolism of 25-hydroxyvitamin D3 to products with modified side-chains involving C-26 and/or C-27. It is possible that this metabolism is responsible for the regulation of kidney cellular concentrations of 25-hydroxyvitamin D3. |
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