Androgen receptors in brain and pituitary of female rats: cyclic changes and comparisons with the male. Biol. Reprod

The in vitro binding of a synthetic androgen, methyltrienolone ([3H]-R 1881), to brain and pituitary (PIT) cytosol and nuclear extracts was determined in male and female rats. Purified cytosol was prepared from P1T or hypothalamic-preoptic area-amygdala (HPA) and incubated in the presence of 0.1 to 10 nM [3H]-R1881. Scatchard analysis revealed the presence of a single, saturable, high-affinity binding site in PIT cytosol with a dissociation constant (Kd) of 0.42 x 10_b M in females and 0.95 x 10_b M in intact males. The Kd of HPA cytosol was much less in castrated males [0.47 ± 0.05 (SEM) x iO#{176} M, n=7] and females (0.63 ± 0.1 x 10_b M, n=4) than in intact males (5.8 ± 1.1 x 10_b M, n=8). Treatment of castrated males with dihydrotestosterone (DHT) for 24 h (250 pg/100 g of body weight) increased the Kd of HPA cytosol only slightly (1.6 x 10_b M, mean of two replicates). Scatchard analysis of salt-extracted nuclear androgen receptor (AR) showed a single, high-affinity binding site with similar Kd values in PIT and HPA of intact and castrated, DHT-treated male rats (PIT Kd = 7.3 x 10_b M, 9.3 X 10#{176} M; HPA Kd = 1.5 x iO M, 1.3 x iO M, respectively). Competition studies involving a range of several radioinert steroids revealed that the binding of [3H]-R 1881 to cytosol (ARe) and nuclear extract was specific for androgen receptor when triamcinolone acetonide (10 pM) was added. The A R and A