Effect of ethanol on follicle stimulating hormone-induced steroidogenic acute regulatory protein (StAR) in cultured rat granulosa cells.
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abstract
Steroidogenic acute regulatory protein (StAR) plays a critical role in trophic hormone-stimulated steroid biosynthesis by facilitating the transfer of cholesterol across the mitochondrial membrane, where the cytochrome P450scc enzyme resides to initiate steroid hormone biosynthesis. Because follicle stimulating hormone (FSH) is a critically important regulator of estradiol (E2) synthesis in granulosa cells and because ethanol is known to suppress gonadotropin-stimulated ovarian steroidogenesis, we evaluated the effects of ethanol on FSH-stimulated StAR in ovarian granulosa cells. Granulosa cells from immature rats pretreated with pregnant mare serum gonadotropin were cultured for 24 h in serum-free medium, either alone (medium only) or with FSH (25 ng/ml) in the presence or absence of ethanol (50 mM). Real-time polymerase chain reaction (PCR) analysis showed increased (p < 0.01) expression of the StAR transcript in FSH-treated cells, when compared with cells that received medium only. The FSH stimulation of StAR transcript was blocked (p < 0.01) by the presence of ethanol. This effect coincided with a decrease in E2 secretion into the culture medium. We also examined whether ethanol could affect the production of cyclic AMP (cAMP), the main second messenger that mediates gonadotropin action within the ovary. FSH treatment of granulosa cells markedly increased (p < 0.001) cAMP levels, an effect that was not altered by ethanol. Importantly, FSH induced an increase (p < 0.01) in the release of prostaglandin E2 (PGE2), an effect that was blocked by ethanol. Real-time PCR analysis showed that ethanol had no effect on the expression of cyclooxygenase-1 (COX-1), but blocked (p < 0.01) FSH-stimulated expression of COX-2. These results demonstrate that ethanol is capable of inhibiting FSH-induced ovarian StAR and thus, contributing to suppressed E2 secretion, at least in part, through an inhibitory action on the COX-2-PGE2 pathway.
