Evidence for the metabolism of 24R-hydroxy-25-fluorovitamin D3 and 1alpha-hydroxy-25-fluorovitamin D3 to 1alpha,24R-dihydroxy-25-fluorovitamin D3. |
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Authors: | J L Napoli W S Mellon H K Schnoes H F DeLuca |
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Affiliation: | Department of Biochemistry, College of Agricultural and Life Sciences, University of Wisconsin-Madison, Madison, Wisconsin 53706 U.S.A. |
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Abstract: | High-pressure liquid chromatography capable of resolving all known vitamin D metabolites and a sensitive competitive binding protein assay specific for 1α,25-dihydroxyvitamin D3 were used to assay the blood of rats dosed with ethanol, 1α-hydroxyvitamin D3, 24R-hydroxy-25-fluorovitamin D3, or 1α-hydroxy-25-fluorovitamin D3. Compared to the ethanoldosed animals, the blood of rats dosed with 1α-hydroxyvitamin D3 had increased levels of 1α,25-dihydroxyvitamin D3; but those dosed with the fluorinated vitamins did not. Instead, their blood contained a compound that cochromatographs with 1α,24R-dihydroxyvitamin D3 on high-pressure liquid chromatography and binds to the 1,25-dihydroxyvitamin D3 receptor proteins. 1α,24R-Dihydroxyvitamin D3 binds as well as 1α, 25-dihydroxyvitamin D3 to the chick-intestinal cytosol receptor protein for 1α,25-dihydroxyvitamin D3; whereas 1α,24S-dihydroxyvitamin D3 binds only one-tenth as well as 1α,25-dihydroxyvitamin D3. Thus it appears that in vivo, the fluorinated vitamin D compounds are converted to a compound likely to be 1α,24R-dihydroxy-25-fluorovitamin D3 and that may rival the potency of 1α,25-dihydroxyvitamin D3. |
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Keywords: | To whom all correspondence should be addressed. |
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