[Effect of human inhibin alpha-fragment 1-32-Tyr(P33) on apoptosis of cultured rat corpus luteal cells].
Recently, increasing evidence suggests that alpha inhibin or related proteins may be a functional regulator in the ovary, which is independent of hetero-dimer inhibin. In our previous study, it was demonstrated that human inhibin alpha-N-terminal fragment Tyr-1-32 (P(33)) significantly inhibited progesterone production by rat corpus luteal cells in vitro, and stimulated luteal functional regression and apoptosis in vivo. In the present work, the action of P(33) on apoptosis was further studied in vitro in cultured rat CL cells. Gel electrophoretic analysis for detection of oligonucleosomal DNA fragmentation, AO-EB or PI assays and flow cytometry were used to observe the action of P(33) on the occurrence of spontaneous apoptosis by collagenase-DNase dispersed CL cells, obtained from PMSG-hCG induced pseudopregnant rats. The results showed that P(33) (1 microg/ml) stimulated spontaneous apoptosis of CL cells. The inhibitor of tyrosine protein kinase, genistein (50 microg/ml),inhibited P(33) enhanced spontaneous apoptosis. RNA and protein synthesis inhibitors cycloheximide (Cyx,50 microg/ml) and actinomycin D(Act D,50 microg/ml) did not protect the cells from apoptosis stimulated by P(33). The results suggest that P(33) stimulates spontaneous apoptosis in cultured rat CL cells with the involvement of tyrosine specific protein kinase system. This work provides further evidence for the hypothesis that alpha inhibin or related protein might be a functional regulator in the ovary.