Effects of gonadectomy and hormone replacement on steroid hormone receptors and 5α-reductase activity in pituitaries of male rhesus macaques

We measured androgen, estrogen, and progestin receptors and 5α-reductase activity in the anterior and posterior pituitary gland of intact and 6-week castrate adult male rhesus monkeys and castrate males which were treated with testosterone (T) or estradiol (E) from time of surgery. Saturation analysis of anterior pituitary tissues from monkeys receiving various treatments revealed an apparent mean dissociation constant (K_d) of 0.53 ± 0.17 (±se) × 10⁻¹⁰ mol/L (n = 3) for [³H]R1881 (androgen) binding to cytosol, 2.6 ± 0.50 × 10⁻¹⁰ mol/L (n = 3) for [³H]R2858 (estrogen) binding to cytosol, 1.7 × 10⁻¹⁰ mol/L (n = 2) for [³H]R5020 (progestin) binding to cytosol, and 6.2 × 10⁻¹⁰ mol/L (n = 2) for [³H]Rl881 binding to cell nuclear extract. The highest levels of nuclear androgen receptor (AR) were found in intact males [37.1 ± 3.5 (±se) fmol/mg DNA; n = 7] and castrated males treated with T for 6 weeks (89.7 ± 30.2 fmol/ mg DNA; n = 5). High levels of nuclear AR corresponded to serum T levels and low serum LH levels. Nuclear AR was undetectable in castrated males and castrated males treated with E. Significantly greater levels of cytosolic AR were detected in intact males (27.5 ± 1.6 fmol/mg protein) compared to all other groups (P < 0.05). T or E treatment had no effect on cytosolic AR. Increased levels of cytosolic progestin receptor were found in intact monkeys and after E or T treatment compared to levels in untreated castrates. No differences in 5α-reductase activity were found between any treatment groups. These data indicate that anterior pituitary nuclear androgen receptor is correlated with serum LH levels and support the hypothesis of a direct action of T on anterior pituitary LH secretion. In addition, it appears that cytosolic progestin receptor, but not AR, is regulated by estrogen in intact male rhesus monkeys. In the posterior pituitary, AR dynamics followed a profile in which cytosolic AR increased after castration and decreased after T treatment. Nuclear AR decreased after castration and increased after T treatment. The presence of a dynamic AR system in the posterior pituitary suggests hormonal regulation of its function by androgens.