The intestinal nuclear receptor for lα,25-dihydroxyvitamin D3 has been utilized to determine the ability of vitamin D-active sterols to compete with this hormone at the molecular level. 25-Hydroxyvitamin D3 and lα-hydroxyvitamin D3 must be present in 150 and 450 times the concentration respectively of lα,25-dihydroxyvitamin D3, in vitro, to displace the physiologic hormone. These data indicate that: i) superphysiologic levels of 25-hydroxyvitamin D3 may simulate lα,25-dihydroxyvitamin D3 and act directly on isolated target organs and ii) the biologic potency observed for low doses of lα-hydroxyvitamin D3, in vivo, is probably the result of 25-hidroxylation of the lα-derivative to form lα,25-dihydroxyvitamin D3.
ASJC Scopus subject areas
- Biochemistry, Genetics and Molecular Biology(all)
- Pharmacology, Toxicology and Pharmaceutics(all)