Inhibitory effect of gossypol on basal and luteinization factor-stimulated progesterone synthesis in porcine granulosa cells.

Gossypol, a polyphenolic aldehyde, inhibits steroidogenesis and the reproductive system in both sexes. The present study was undertaken to investigate whether gossypol may affect progesterone biosynthesis in cultured porcine granulosa cells isolated from small (1-2 mm) follicles (SGC). SGC were cultured with gossypol, NO donor S-nitroso-N-acetylpenicillamine (S-NAP) or the specific NO-synthase inhibitor N-nitro-L-arginine methyl ester (L-NAME), in the presence or absence of follicular fluid isolated from large (5-8 mm) follicles (LFF) or conditioned media (CM) of granulosa cells isolated from large follicles (LGC). Gossypol enhanced the nitrite content in culture media of SGC and inhibited basal progesterone secretion by SGC. S-NAP (10(-3) M) inhibited progesterone secretion and enhanced the formation of cGMP by SGC. L-NAME had no effect on progesterone accumulation by SGC. The stimulatory effect of LFF or CM media on progesterone production by SGC in culture was also inhibited by S-NAP (10(-3)) and gossypol (10(-4) M). Moreover, gossypol inhibited forskolin-stimulated progesterone secretion, as well as substrate-enhanced conversion of 22-OH-cholesterol and pregnenolone to progesterone. These results suggest that the inhibitory effect of gossypol on progesterone secretion in culture of SGC may be mediated via NO generation.