Nuclear estrogen receptor bindings in granulosa cells and estradiol-17 beta contents in follicular membranes of the ovary of the hen during the ovulatory cycle

Estrogen receptors were found in the nuclear fractions of granulosa cells of the largest (F 1 ) and the second largest (F 2 ) preovulatory follicle in the ovary of the hen. The maximum number of binding sites (NBSmax) of the nuclear estrogen receptors was greater in F 2 than in F 1 , while the equilibrium dissociation constant ( K d ) was not different. During the ovulatory cycle, the NBSmax of the estrogen receptors showed a change parallel to the change in the estradiol-17β content in the follicular membranes. The results suggest that estradiol-17β produced in the follicular membrane may exert a direct action on the granulosa cells in the hen ovary.