Specific high affinity binding sites for [3H]1α, 25-dihydroxy-vitamin D3 were observed in nuclear fractions of rat pituitary adenoma GH3 cells. Crude nuclear (P1) sites demonstrated a pharmacological specificity for vitamin D3 metabolites and analogues that was in accord with the characteristics of 1α, 25-dihydroxyvitamin D3 receptors in recognized target organs. GH3 cells grown in serum-containing medium contained significant amounts of 1α, 25-dihydroxy-vitamin D3 in a P1 extract, whereas no 1α, 25-dihydroxyvitamin D3 was detectable in P1 extracts from cells cultured in the absence of serum. Binding of [3H]1α, 25-dihydroxyvitamin D3 to the P1 fraction was unaffected by prior depletion of intracellular 1α, 25-dihydroxyvitamin D3, suggesting that association of [3H]1α, 25-dihydroxyvitamin D3 to nuclear sites is not attributable to translocation of a cytosolic hormone-receptor complex and molecular exchange. The results support the concept that 1α, 25-dihydroxyvitamin D3 has a physiological role in mediating pituitary hormone secretion.
ASJC Scopus subject areas
- Biochemistry, Genetics and Molecular Biology(all)
- Pharmacology, Toxicology and Pharmaceutics(all)