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Synthesis of 24S and 24R-hydroxy-[24-3H]vitamin D3 and their metabolism in rachitic rats

1976; Elsevier BV; Volume: 177; Issue: 2 Linguagem: Inglês

10.1016/0003-9861(76)90473-2

1096-0384

Yoko Tanaka, Hector F. DeLuca, Akira Akaiwa, Masuo Morisaki, Nobuo Ikekawa,

Adrenal Hormones and Disorders

An epimeric mixture of 24-hydroxy-[24-3H]vitamin D3 was synthesized by the reduction of 24-ketovitamin D3 by sodium borotritide. The epimeric mixture was converted to the trimethylsilylether derivatives and subjected to high-pressure liquid chromatography using silica gel columns to separate the 24-hydroxy-[24-3H]vitamin D3 isomers. The 24R-hydroxy-[24-3H] vitamin D3 induced calcification in rachitic rats while the 24S-hydroxy-[24-3H] vitamin D3 had little or no such activity. As both isomers of 24-hydroxy-vitamin D3 are metabolized to 24,25-dihydroxyvitamin D3, it appears that the 24-hydroxyvitamin D3-25-hydroxylase does not discriminate between the isomers. Only the R-isomer of 24-hydroxyvitamin D3 is metabolized to 1,24-dihydroxyvitamin D3, although only trace amounts of this compound were found 2 days after the administration of 24-hydroxyvitamin D3. The striking difference in the metabolism of the isomers is the high selectivity of the 1-hydroxylase for R-isomer. It is suggested that the high specificity of biological activity for the R-isomer of 24-hydroxyvitamin D3 is because of the specificity of the 1-hydroxylation of 24,25-dihydroxyvitamin D3 for the R configuration.