A receptor-like testosterone-binding protein in ovaries from estrogen-stimulated hypophysectomized immature female rats.

A soluble thermolabile protein with many characteristics of an androgen receptor has been demonstrated for the first time in the cytosol (100,000 X g supernatant) of estrogen-stimulated ovaries from hypophysectomized immature female rats (HIFR) treated with diethylstilbestrol in Silastic capsules (DESC). This binding protein is organ-specific and androgen-specific, has a high affinity with a Kd of 2.4 X 10(-9)M for testosterone, and is saturable with 2.1 X 10(-13) moles of binding sites per mg cytosol protein. The number of binding sites is linear with cytosol protein concentration and the binding protein sediments at 7-8 S on sucrose gradients. Estradiol is an effective inhibitor of testosterone binding. A role for this testosterone-binding protein as an effector of ovarian morphologic change is hypothesized.