LOCALIZATION OF PROGESTERONE RECEPTORS IN PREOVULATORY AND POSTOVULATORY FOLLICLES OF THE DOMESTIC HEN

Progesterone may act locally to modulate follicular maturation and ovulation in the domestic hen. The distribution of progesterone receptors (PR) in the pre- and postovulatory follicles was determined in hens by immunocytochemistry and Western blot analysis. Monoclonal antibodies to chicken PR, PR6, and PR 13, were used. PR were localized in nuclei of theca externa fibroblasts and germinal epithelial cells in stigma and nonstigma regions of the third largest preovulatory follicle (F3). In the largest preovulatory follicle (F1), PR were present in theca externa fibroblasts, germinal epithelial cells, and also in granulosa cells and some of the theca interna fibroblasts in the stigma and nonstigma region. Twenty-four hours after ovulation, PR in the fibroblasts of the theca externa of the postovulatory follicle (POF) were remarkably reduced, but the amount of PR in the granulosa cells was similar to that observed in the F1. A high density of PR was also found in the fibroblasts, arterial wall, and smooth muscle fibers in the loose connective tissue of pre- and postovulatory follicles. Western blot analysis indicated that PR in the granulosa and theca tissue were identical in molecular weight to PR in the shell gland. Western blot analysis also confirmed the changes in the amounts of PR in the pre- and postovulatory follicles as determined by immunocytochemistry. The relative amounts of PR in the granulosa cells as determined by Western blot analysis was F2 < F1 = POF, and in theca tissue was F2 = F1 > POF. The presence of PR in specific ovarian tissues suggests that these tissues are target tissues for progesterone and that progesterone may have a role in regulating follicular maturation and ovulation through receptor-mediated pathways.