Specific binding of 1α,25-dihydroxyvitamin D3 to macromolecular components of small intestinal nuclei and cytosol is demonstrated. The nuclear 1α,25-dihydroxyvitamin D3 complex can be extracted from chromatin by 0.3 M KCl and sediments at 3.7S in sucrose density gradients. The cytoplasmic 1α,25-dihydroxyvitamin D3-binding components also sediment at 3.7S, identically to the nuclear complex under the ultracentrifugation procedures employed. Macromolecular binding components with a high affinity for 25-hydroxyvitamin D3 (Kd = 4.5 × 10-9 M) were also identified in intestinal cytosol which differ from the 1α,25-hydroxyvitamin D3 receptor in that: 1) they sediment at 5-6S in sucrose gradients, 2) they are observed in organs other than the intestine, and 3) while they do bind 1α,25-dihydroxyvitamin D3 at higher concentrations than 25-hydroxyvitamin D3, they are not observed to transfer either 25-hydroxyvitamin D3 or 1α,25-dihydroxyvitamin D3 to the nucleus, in vitro.
ASJC Scopus subject areas
- Biochemistry, Genetics and Molecular Biology(all)
- Pharmacology, Toxicology and Pharmaceutics(all)