Abstract
The maximum number of binding sites of cytoplasmic progesterone receptors in the oviduct uterus (Shell gland) was greater in laying hens than in nonlaying hens when compared on the tissue basis, while the value of equilibrium dissociation constant was not significantly different. The content of cytoplasmic progesterone receptors, expressed as the amount of specific [3H]pro- gesterone bindings per tissue, in the oviduct uterus of laying hens was found to change during the ovulatory cycle, showing a peak at 8h, 18h and 23h after ovulation. In contrast, no appre- ciable change was found during a 24-h day in nonlaying hens.
