Gonadotropins enhance caspase-3 and -7 activity and apoptosis in the theca-interstitial cells of rat preovulatory follicles in culture.

Apoptosis causes the elimination of ovarian germ cells and the atretic degeneration of ovarian follicles. Here we have used cultured rat preovulatory follicles to examine the regulation of effector caspase-3 and -7 in follicles undergoing apoptosis in the presence or absence of gonadotropins or IGF-I. Culturing follicles in the presence or absence of serum resulted in the induction of apoptosis of granulosa cells (GC), which was accompanied by effector caspase activation. Surprisingly, the addition of the survival factors LH or FSH, but not IGF-I, further increased caspase-3 and -7 activity. Immunohistochemistry studies of the LH- and FSH-treated follicles indicated that cleaved caspase-3 was predominantly localized to the peripheral theca-interstitial cells (TIC). Western blot analysis and caspase-3 and -7 activity assays of the separated follicular compartments confirmed that both LH and FSH treatments significantly enhance caspase-3 and -7 activity in TIC. The elevation in caspase-3 and -7 activity in TIC was accompanied by an increase in apoptosis. Interestingly, LH and FSH also induced an increase in caspase-3 and -7 activity in GC; however, this increase was accompanied by a decrease in apoptosis. Finally, we demonstrate that in freshly isolated preovulatory follicles and in antral follicles in intact ovaries, the expression level of procaspase-3 is significantly higher in TIC than in GC. Thus, LH and FSH have a dual effect on the cultured rat preovulatory follicle: an antiapoptotic effect on GC and a proapoptotic effect on TIC.