Chicken postovulatory follicle (POF) regression occurs via the process of apoptosis. However, the signals and initiator pathways responsible for regression of the POF are unknown. In the current study, we examined gene expression patterns of various
caspases (caspase-1, -2 and -3) involved in apoptosis by semi-quantitative RT-PCR. The percentage of apoptotic cells during POF regression was also quantified by flow cytometry. Expression of
caspase-3 mRNA was noted in the largest preovulatory follicle (F1). However, the
initiator caspases (caspase-1 and -2) were not expressed in F1. During the regression of the POF,
caspase-3 was activated during initial stages, whereas the
initiator caspases were upregulated at the later stages (POF4 and
POF5). The percentage of apoptotic cells was significantly higher during the regression of the POF. It might be possible that levels of
caspase-3 mRNA do not necessarily reflect the cell's potential for facilitating apoptosis, as activation of the
caspase-3 by
initiator caspases is required for its function. We presume that both caspase-1 and
caspase-2 were key initiators in the regression of chicken POF and that the apoptosis-mediated regression of POFs might be similar to mammalian corpus luteum involution.