Purification and Characterization of 1,25(OH)₂D₃ Receptor from Human Placenta

OBJECTIVE: To characterize the receptor for 1,25-dihydroxycholecalciferol [1,25-(OH)2D3], we purified it from nuclear fractions of human placentae. METHODS: Human placental fractions were concentrated with ammonium sulfate, extracted from hydroxylapatite, and then chromatographed on Sepharcryl S-200 and DEAE-cellulose. RESULTS: The receptor for [1,25(OH)2D3] was purified approximately 1,500-fold. The molecular weight of the receptor was estimated to be 55 K dalton by gel filtration. The receptor fractions showed a dissociation constant (Kd) of 3.0 x 10(-10) mol/l, and adsorbed to the DNA cellulose column. D3 analogs, estradiol, and progesterone had almost no effect on 1,25(OH)2D3 binding. CONCLUSION: These properties of the 1,25(OH)2D3 receptor in human placenta are similar to those of the chicken intestinal 1,25(OH)2D3 receptor.