GLUCAGON-STIMULATED CYCLIC-AMP PRODUCTION AND FORMATION OF ESTRADIOL IN SERTOLI-CELL CULTURES FROM IMMATURE RATS

Addition of glucagon to the incubation medium of cultured Sertoli cells isolated from immature (19-day-old) rats resulted in a time- and concentration-dependent stimulation of cAMP accumulation measured both in the cells and in the medium. Maximal intracellular levels of cAMP were reached after 30 min, after which the levels decreased. In the medium cAMP levels reached a plateau after 6 h. The magnitude and kinetics of the responses were comparable to those observed with FSH in the same culture preparations. 1-Methyl-3-isobutylxanthine (MIX), a phosphodiesterase inhibitor, greatly potentiated the magnitude of the effects of glucagon and FSH. Glucagon stimulated adenylate cyclase activity in isolated membrane preparations from similar cultures, and the concentration causing half-maximal stimulation (EC50) was .apprx. 300 ng/ml. Glucagon also stimulated aromatization in cultured Sertoli cells to the same extent as FSH. Cultured Sertoli cells isolated from immature rats contain receptors for glucagon, coupled to adenylate cyclase. Glucagon also stimulates aromatization of testosterone to estradiol.