Increase in catecholamine-stimulated cyclic AMP and progesterone synthesis in rat granulosa cells during culture

Abstract

Catecholamines stimulated cyclic AMP and progesterone synthesis in rat corpora lutea but not in the pre-ovulatory follicles. We collected granulosa cells from follicles of immature rats treated with pregnant mare's serum gonadotropin (PMSG) and cultured them either in monolayer or in suspension. Freshly collected granulosa cells responded to isoproterenol and epinephrine with 2-fold increases in cyclic AMP accumulation and progesterone synthesis. However, granulosa cells cultured in monolayer for 2 days responded to isoproterenol and epinepherine with a 90-fold and a 6-fold increase in cyclic AMP accumulation and progesterone synthesis, respectively. The accumulation of cyclic AMP in response to Catecholamines gradually increased in cells cultured in suspension, from 2-fold over control after 5 h, to 8-fold after 24 h. Granulosa cells isolated from hypophysectomized and diethylstilbestrol (Hx-DES) treated immature rats (containing pre-antral follicles) also showed an increase in cyclic AMP accumulation in response to Catecholamines during culture. Because these cells are devoid of an LH-responsive adenylate cyclase system, we conclude that luteinization of granulosa cells in culture is not necessarily the process responsible for the increased response to Catecholamines. During culture, the number of β-adrenergic receptors in granulosa cells rose from 6020 ± 400 per 10 6 cells shortly after isolation to 26400 ± 1800 after 2 days in culture. This increase in receptor density during culture may be responsible for the change in the responsiveness to Catecholamines, although other factors, such as changes in coupling efficiency between the hormone-receptor complex and the adenylate cyclase moiety and/or supersensitivity to Catecholamines, should also be considered.