Characterization of androgen-binding protein in the human ovarian capsule and its changes by polycystic ovarian disease.

In sucrose density gradient analysis, the cytosol of human ovarian capsules was found to contain two (3H)dihydrotestosterone (DHT)-binding macromolecules with sedimentation constants of 9S and 4.6S, respectively. In the tissue, however, more than 95% of the total (3H)DHT binding to the cytosol was found to be due to the 4.6S macromolecule. This molecule was further characterized and identified as a tissue-specific androgen-binding protein (ABP). The dissociation constant and number of binding sites of ABP were 2.60 nM and 231 fmol/mg protein, respectively. ABP was further characterized by affinity chromatography on concanavalin A-Sepharose and was found to separate into two parts: one showed no interaction with the resin and was eluted in the void volume (peak I) and the other bound to the resin and was eluted by alpha-methyl-D-glucoside (peak II). The apparent amount of cytoplasmic ABP in capsules with polycystic ovarian disease was significantly lower than normal. This decrease in ABP was mainly due to the characteristic disappearance of peak II.