Effects of progesterone, estrogen, and androgen on progesterone receptor binding in hen oviduct uterus (shell gland).

The specific [3H] progesterone binding per milligram of protein of the cytosolic fraction of the hen uterus was found to have decreased at 1 and 4 h after the injection of progesterone (P4), but increased at 4 and 8 h after the injection of estradiol-17 beta (E2), and at 1 and 4 h after the injection of testosterone (T). The equilibrium dissociation constant obtained by Scatchard analysis was not significantly different between the hens receiving steroid injections [P4], E2, T, and dihydrotestosterone (DHT)] and controls. The maximum binding capacity was lower in hens injected with P4 and greater in hens injected with E2, T, or DHT than in uninjected hens. The results suggest that the cytosolic progesterone receptor binding in the hen uterus may be modulated by the sex steroid hormones.