Abstract:
Apoptosis is associated with regression of corpora lutea (CL) in a number ofspecies. The present work compared apoptotic rates, assessed by low molecularweight DNA labelling, in rat CL of the oestrous cycle, pregnancy, theimmediate post-partum period, and in vitro culture.Apoptosis was significantly related to cycle phase with peak activity atoestrus. This pattern was similar in CL formed from the most recent ovulationand from the two previous generations. Apoptosis was evident during pregnancy,albeit at low rates. It declined on the day of parturition and increased onthe following day. Apoptosis was greatly increased in cultured CL to reach20-fold higher levels than those achieved during the oestrous cycle orpregnancy. Collectively, these results suggest that apoptosis has lessersignificance in rat CL functional regression than in other species with moreprecipitate structural changes. However, rat CL clearly retain the potentialfor high rates of apoptosis and so present a useful model for examiningmolecular mechanisms of apoptotic cell death.Extra keywords: luteal regression, ovulation, humanchorionic gonadotrophin, cell death.