S. Matsuyama et al., OCCURRENCE OF DEOXYRIBONUCLEIC-ACID FRAGMENTATION DURING PROLACTIN-INDUCED STRUCTURAL LUTEOLYSIS IN CYCLING RATS, Biology of reproduction, 54(6), 1996, pp. 1245-1251
We determined whether fragmentation of genomic DNA, one of the hallmar
ks of apoptosis, occurs during structural luteolysis in cycling rats.
Corpora lutea (CL) were collected from rats at each estrous cycle stag
e (1800 h), and fragmented DNA was extracted. Only CL from rats at the
proestrous stage showed distinct DNA fragmentation. To determine the
period of occurrence of DNA fragmentation, CL were collected at severa
l points between 1200 h on the day of proestrus and 0600 h on the day
of estrus. Distinct DNA fragmentation was observed from 1800 h (proest
rus) to 2400 h (proestrus), and the extent was significantly lower at
0600 h (estrus). It is known that prolactin (PRL) induces structural l
uteolysis in rats. To examine the role of PRL in luteal DNA fragmentat
ion, 2-bromo-alpha-ergocryptine (BE) was used to suppress the PRL surg
e on the day of proestrus. CL collected at 1800 h from BE-treated rats
did not show distinct DNA fragmentation, and PRL injection offset the
effect of BE. Histochemical analysis with a 3'-end labeling technique
confirmed the occurrence of DNA fragmentation in luteal tissue. These
results suggest that apoptotic cell death occurs during PRL-induced s
tructural luteolysis.