Metabolism of 1alpha,25-dihydroxyvitamin D(3) in vitamin D receptor-ablated mice in vivo.
The metabolism of 1alpha,25-dihydroxyvitamin D(3) was studied in vitamin D receptor-ablated mice following the administration of a physiological dose of 1alpha,25-dihydroxy-[26,27-(3)H]vitamin D(3). The degradation of 1alpha,25-dihydroxy-[26,27-(3)H]vitamin D(3) in the vitamin D receptor null mutant mice was substantially reduced compared to the wild-type control mice. At 24 h postadministration of radiolabeled 1alpha,25-dihydroxyvitamin D(3) more than 50% of the radioactivity was recovered unmetabolized, whereas in wild-type mice nearly all of the 1alpha,25-dihydroxy-[26,27-(3)H]vitamin D(3) was degraded. In wild-type mice three polar metabolites other than 1alpha,25-dihydroxyvitamin D(3) were detected and identified on straight-phase and reverse-phase high-performance liquid chromatography as 1alpha,24(R),25-trihydroxy-[26,27-(3)H]vitamin D(3), 1alpha,25(S),26-trihydroxy-[26,27-(3)H]vitamin D(3), and (23S, 25R)-1alpha,25-dihydroxy-[(3)H]vitamin D(3)-26,23-lactone. Only one metabolite was detected in the plasma and kidneys of vitamin D receptor null mutant mice at 3 h following an intrajugular dose of 1alpha,25-dihydroxy-[26,27-(3)H]vitamin D(3). This metabolite was clearly identified as 1alpha,25(S),26-trihydroxy-[26,27-(3)H]vitamin D(3) by comigration on two HPLC systems and periodate cleavage reaction. At 6, 12, and 24 h postinjection 1alpha,24(R), 25-trihydroxy-[26,27-(3)H]vitamin D(3) was also detected at low levels in plasma, kidneys, and liver of some but not all mutant mice. The presence of 25-hydroxyvitamin D(3)-24-hydroxylase mRNA in the kidneys of these vitamin D receptor null mutant mice was confirmed by ribonuclease protection assay.
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Department of Biochemistry, University of Wisconsin-Madison, 433 Babcock Drive, Madison, Wisconsin 53706, USA.
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DeLuca
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D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D002117:Calcitriol / Q000008:administration & dosage / Q000378:metabolism*; D002118:Calcium / Q000097:blood; D002851:Chromatography, High Pressure Liquid; D007668:Kidney / Q000378:metabolism; D050356:Lipid Metabolism; D008099:Liver / Q000378:metabolism; D051379:Mice; D008817:Mice, Mutant Strains; D008934:Mitogens / Q000494:pharmacology; D010504:Periodic Acid / Q000494:pharmacology; D010710:Phosphates / Q000097:blood; D012333:RNA, Messenger / Q000378:metabolism; D018167:Receptors, Calcitriol / Q000502:physiology*; D013997:Time Factors
D008934:Mitogens; D010710:Phosphates; D012333:RNA, Messenger; D018167:Receptors, Calcitriol; D010504:Periodic Acid; C009288:metaperiodate; D002117:Calcitriol; D002118:Calcium