Differential Effects of Luteinizing Hormone-Releasing Hormone on Follicle-Stimulating Hormone-Dependent Responses in Rat Granulosa Cells and Sertoli Cells in Vitro*

Abstract

The abilities of LHRH and a potent LHRH agonist ([D-Ser-(Bu^t)⁶, des-Gly-NH₂¹⁰]LHRH ethylamide) to inhibit FSH responses by rat granulosa cells and Sertoli cells in vitro have been compared. Granulosa cells isolated from 22- or 25-day-old diethylstilbestrol-primed rats and cultured under defined conditions for 48 h with NIH-FSH-S13 (300 ng/ml) or cholera toxin (0.1 μg/ml) showed increased aromatase activity, as determined by the release of ³H₂O from [1β-³H]testosterone. LHRH (10^-7 M) or the agonist (10^-8 M) added simultaneously with FSH or cholera toxin inhibited the effects on the release of ³H₂O without influencing the protein content of the cell cultures. A smaller stimulation of ³H₂O production occurred with (Bu)₂cAMP (1.0 mM) plus 3-isobutyl-l-methylxanthine (0.1 mM), and this was partially suppressed in the presence of LHRH or the agonist. Parallel studies with Sertoli cells from 15- or 20-day-old rats demonstrated that culture under appropriate conditions with FSH, cholera toxin, or (Bu)₂cAMP (0.5 mM) for 24 h caused an increase in cellular aromatase activity and enhanced secretion into the medium of plasminogen activator. However, no inhibition by LHRH (10^-7 or 10^-9 M) or the agonist (10^-6 or 10^-8 M) occurred when the peptides were added either simultaneously or 24 h before the stimulatory agent. Similarly, Sertoli cells from 11-day-old rats treated daily with LHRH agonist for 5 days in culture, showed no inhibition of aromatase activity after a 4-h stimulation with FSH or (Bu)₂cAMP. FSH dose-response curves (0-300 ng/ml) for aromatase activity were shown to be similar after 5 days of culture with or without 10^-8 M LHRH agonist, indicating that the LHRH did not cause a shift in the sensitivity to FSH. The lack of inhibition was seen in Sertoli cell cultures maintained at 37 or 32 C. The enzyme digestion method used to isolate Sertoli cells was not responsible for the lack of effects of LHRH, since cell cultures prepared without the aid of proteolytic enzymes showed similar FSH stimulation of aromatase activity in the presence or absence of 10^-8 M agonist. Further, there was no evidence of degradation of the LHRH agonist when incubated with Sertoli cell cultures. From these studies, we conclude that 1) granulosa cells and Sertoli cells from immature rats differ in their responses to LHRH, and 2) the immature Sertoli cell is an unlikely target for a direct inhibiting influence of LHRH on spermatogenesis. (Endocrinology108: 812, 1981)