The Ovary: A Target Organ for 1,25-Dihydroxyvitamin D3*

Abstract

Using both clonal Chinese hamster ovary (CHO) cells in culture and the hen ovary, we have searched for the presence of specific 1,25-dihydroxyvitamin D₃ [1,25-(OH)₂D₃] receptors. Receptor analyses were carried out on high salt cytosols of CHO cells and high salt extracts of hen ovarian nuclei that were originally isolated in low salt buffer. Both CHO and hen ovary contain a specific high affinity 1,25-(OH)₂D₃ receptor (K_d= 10^-10-10^-11 M), which sediments (3.3S) in high salt sucrose gradients identically to the chick intestinal receptor for 1,25- (OH)₂D₃. This 3.3S macromolecule from both sources adsorbed to DNA-cellulose at 0.1 M KC1 and eluted during a linear salt gradient at 0.2–0.22 M KCl, a property characteristic of the 1,25- (OH)₂D₃ receptor. Saturation analysis indicated that there are approximately 2000 copies of the receptor molecule per CHO cell. We also investigated the effect of 1,25-(OH)₂D₃ on ovarian cell growth in monolayer culture of CHO cells. Significant inhibition of CHO cell growth (up to 60%) was observed in the presence of physiological (100 pM) levels of 1,25-(OH)₂D₃ in the culture medium. This inhibition of growth was dose dependent and was accompanied by a parallel decrease in total cell protein. Concentrations of 25-hydroxyvitamin D₃ and 24,25-dihydroxyvitamin D₃ as high as 1 nM did not affect CHO cell growth, indicating that, like receptor binding, cell proliferation is selectively influenced by 1,25-(OH)₂D₃ over other vitamin D metabolites. These data demonstrate that ovarian cells in mammals and birds possess the 1,25-(OH)₂D₃ receptor which may play a role in the effect of 1,25-(OH)₂D₃ on the growth of these cells in culture.