Cytoplasmic Progesterone Receptor Concentrations in the Hen Hypothalamus and Pituitary: Difference between Laying and Nonlaying Hens and Changes during the Ovulatory Cycle

The maximum number of binding sites per mg protein of cytoplasmic progesterone receptors in the hypothalamus and pituitary was greater in laying hens than in nonlaying hens, while the value of equilibrium dissociation constant did not differ significantly. The concentration of the cytoplasmic progesterone receptors in the hypothalamus and pituitary showed 2 peaks during the ovulatory cycle: 1 at 8 h before ovulation and the other at 18 h before ovulation.