Further characterization of a rat ovarian testosterone receptor with evidence for nuclear translocation.

We have recently described receptor like testosterone (T)-binding protein in the cytosol of ovaries from estrogen-primed hypophysectomized immature female rats (HIFR). This binding protein is thermolabile, saturable, specific for T, and sediments at 7-8 S on sucrose gradients. We now report the further characterization of this protein. It is present in the cytosol of isolated granulosa cells, has a molecular weight of 240,000, a frictional ratio of 1.8, and a mean Stokes radius of 73 A. The binding protein is acidic and cysteine residues are necessary for binding. We have also demonstrated the selective nuclear accumulation of T by granulosa cells after the in vivo administration of (3H)T to estrogen primed HIFR. After the in vitro incubation of the ovaries with (3H)T, a thermolabile protein specific for T was extracted from nuclei under high-salt conditions. The cytosol and nuclear T-binding proteins described in this report have many characteristics of an androgen receptor, and may play a role in the regulation of granulosa cell proliferation during preantral follicular growth.