Luteinizing hormone-releasing hormone receptor bindings of the hen pituitary: difference between laying and nonlaying hens, effects of ovarian steroid hormones in vivo, and changes during an ovulatory cycle.

The equilibrium dissociation constant (Kd) of the pituitary luteinizing hormone-releasing hormone (LHRH) receptors and the maximum binding capacity (Bmax) per milligram of membrane protein were greater in laying hens than in nonlaying hens. A single i.m. injection of progesterone, estradiol-17 beta, or 5 alpha-dihydrotestosterone into nonlaying hens caused an increase in Kd and Bmax values. During an ovulatory cycle of the laying hen, Kd and Bmax values decreased from 16 to 14 h and 8 to 6 h before ovulation. A decrease in the Bmax value was also found 24 to 21 h before ovulation. A single i.v. injection of chicken LHRH-I caused a decrease in the Kd and Bmax values within 2 min after the injection. The results suggest that the hen pituitary LHRH receptor bindings are affected by ovarian steroid hormones and that their changes during the ovulatory cycle may relate to the release of a gonadotropin from the pituitary.