Distribution of apoptosis-related proteins in the quail ovary during folliculogenesis: BCL-2, BAX and CPP32

It is suggested that follicular apoptosis is driven by the status of the BCL-2: BAX rheostat, and that CPP32 is a key effector of granulosa cell death. In the present study, we have immunohistochemically localized two BCL-2 family members, BCL-2 and BAX, and one caspase, CPP32, in the quail ovary during folliculogenesis. BCL-2 was predominantly found in the granulosa cells of developing follicles. BAX was detected in some follicular cells of atretic follicles, and in the nucleus of some prelampbrush oocytes. Expression of CPP32 was detected in leukocytes and in follicular cells of atretic follicles. Immunostaining was also found in interstitial cells, in surface epithelial and vascular endothelial cells, and in some thecal cells of post-ovulatory follicles. In the granulosa cells of non-growing and small prehierarchal follicles, a weak immunostaining was observed. We can conclude that in the avian ovary, BAX and CPP32 are involved in atresia. The present results support the BCL-2: BAX rheostat hypothesis.