Effects of Gonadotropins and Their Second Messengers on the Induction of Progesterone Receptor in Chicken Granulosa Cells in Vitro: Evidence for Its Dependency on Luteinizing Hormone and Cyclic AMP and Relationship to Follicular Growth.

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Induction of progesterone receptor (PR) in granulosa cells is important for the final events of follicular maturation. Our goal was to determine the mechanism by which PR in the granulosa cells is induced. The effects of gonadotropins and their major second messengers in the induction of PR in the granulosa layer perfused in vitro for 4h were analyzed by Western blotting. No immunoprecipitates for PR were observed in the granulosa cells of the largest follicle (20-22h before ovulation) and smaller ones without hormonal substances (the second plus third largest follicles). Three bands positive for PR, approximately 70K, 80K and 110K Da, were observed in the granulosa cells of the largest follicle and smaller ones stimulated with 0.1μg/ml LH. The granulosa cells of the largest follicle treated with 1mM dibutyryl cyclic AMP (dbcAMP) showed a PR positive band of approximately 70K Da, whereas those of smaller follicles did not. Stimulation of granulosa cells by 2mM dbcAMP induced PR of approximately 70K, 80K and 110K Da in the largest follicle, but not in smaller follicles. No immunostaining was observed in the granulosa cells of the largest follicle and smaller ones stimulated with FSH or phorbol-12-myristate-13-acetate which activates protein kinase C. We suggest that PR is induced by LH via cAMP-mediated pathway and this PR induction is more prominent in the largest follicle than in smaller ones.
日本家禽学会の論文