Cytokine modulation of inhibin secretion in cultured rat granulosa cells

In the present study, we examined the effects of tumour necrosis factor alpha (TNF alpha) and interleukin-1 beta (IL-1 beta) on inhibin secretion by cultured rat granulosa cells using immunoblotting and two-site enzyme immunoassay for inhibin A (alpha-beta A dimer). FSH stimulated the secretion of the inhibin alpha-beta A dimer (32 kDa) by the cells in a dose-dependent manner. In addition to the predominant 32 kDa inhibin alpha-beta A dimer staining, staining of minor immunoreactive bands was also enhanced by FSH. TNF alpha alone did not have any effect on inhibin secretion. Immunoblot analyses using an antiserum against alpha-subunit and an antiserum against beta A-subunit revealed a dose-dependent inhibition by TNF alpha of FSH-stimulated secretion of inhibin by rat granulosa cells. Similarly, TNF alpha inhibited in a dose-dependent manner FSH-stimulated inhibin secretion when measured using a two-site enzyme immunoassay. IL-1 beta alone did not exert any effect on inhibin secretion but it inhibited FSH-stimulated inhibin release in a dose-dependent manner (using both immunoblotting and a two-site assay for inhibin A). The present observations suggest that TNF alpha and IL-1 beta inhibit gonadotrophin-stimulated inhibin production by cultured rat granulosa cells.