OBJECTIVETo study the effects of gonadotroph-releasing hormone (GnRH) agonist (GnRH-a) and GnRH antagonist (GnRH-ant) on cyclophosphamide (CTX)-induced follicle apoptosis in female rats.

METHODSThirty-six female Sprague- Dawley rats were randomized into 6 groups, namely normal saline (NS), CTX, GnRH-a+NS, GnRH-a+CTX, GnRH-ant+NS, and GnRH-ant+CTX groups. The rats were sacrificed between the first and second week after the treatments., and the follicle apoptosis was investigated using TUNEL assay and transmission electron microscopy.

RESULTSThe apoptosis rate of the granulose cells in the follicles in late development was significantly higher than that in early follicles, and the apoptosis rate of the oocytes and granulose cells in rats with CTX treatment was significantly higher than that in rats without CTX treatment (P<0.05). The apoptosis rate of the granulose cells in GnRH-a groups (ranging from 33.40 - or + 4.59 to 73.25 - or + 5.35) was significantly higher than that in GnRH-ant groups (27.46 - or + 4.52 to 49.38 - or + 5.02, P<0.05), but there was no significant difference in the oocytes of early follicles between GnRH-a groups (23.48 - or + 4.25 to 36.15 - or + 4.23) and GnRH-ant groups (21.47 - or + 3.81 to 34.04 - or + 5.54, P>0.05). Electron microscopy revealed characteristic apoptotic changes of the oocytes in early follicles and granulose cells in early and late follicles. The apoptotic changes were especially typical in the granulose cells showing the formation of the apoptotic bodies, and the oocytes only showed chromatin condensation and aggregation.

CONCLUSIONIn the rat mode, GnRH-a promotes while GnRH-ant suppressed follicle apoptosis induced by CTX. GnRH analogues regulates mainly granulose cell apoptosis, but have little effect on oocyte apoptosis.