1,25-dihydroxycholecalciferol: the metabolite of vitamin D responsible for increased intestinal calcium transport |
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Authors: | C A Frolik H F Deluca |
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Institution: | Department of Biochemistry, College of Agricultural and Life Sciences, University of Wisconsin, Madison, Wisconsin 53706 USA |
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Abstract: | 1,25-Dihydroxycholecalciferol was prepared from 26,27-3H]-25-hydroxycholecalciferol and from 1,2-3H]-25-hydroxycholecalciferol enzymatically and purified chromatographically. Injection of 62.5 pmoles of 1,25-dihydroxycholecalciferol intravenously into vitamin D-deficient chicks resulted in the accumulation of a maximum of 5.9% of the dose in the intestine. During the 12 hr period following injection, this radioactivity was found almost entirely as 1,25-dihydroxycholecalciferol. It has previously been shown that intestinal calcium absorption is initiated by 1,25-dihydroxycholecalciferol during this period. These results provide strong evidence that the 1,25-dihydroxycholecalciferol is not metabolized further before it initiates intestinal calcium absorption. |
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