Association of expression of mRNA encoding the PGF2 alpha receptor with luteal cell apoptosis in ovaries of pseudopregnant mice.

The relationship between the expression of mRNA encoding the prostaglandin F2 alpha (PGF2 alpha) receptor and luteal cell apoptosis as determined by oligonucleosome formation was determined in mouse corpora lutea on days 2 (early phase), 6 (mid-phase), and 11 and 13 (late phase) of pseudopregnancy. No signals for mRNA encoding the PGF2 alpha receptor were detected in the ovary as shown by RNA blot analysis of pregnant mares' serum gonadotrophin (PMSG)-treated mice. The expression of the mRNA that could be detected in the corpora lutea on day 2 after hCG treatment was low, but it was increased on day 6 and reached a plateau on days 11 and 13. On days 11 and 13, in situ hybridization signals for mRNA encoding the PGF2 alpha receptor were localized to large luteal cells of the corpora lutea, especially the cells in the superficial layer. However, ethidium bromide staining revealed marked oligonucleosome formation in the corpora lutea on days 11 and 13. Similarly, positive signals of in situ nick-DNA-end labelling were also detected in the corpora lutea on days 11 and 13. Analysis of the adjacent sections of the corpora lutea on day 13 showed that both signals for DNA strand breaks and mRNA encoding the PGF2 alpha receptor were co-expressed in the corpus luteum. These results suggest that apoptosis during structural luteolysis closely associates with the increased expression of mRNA encoding the PGF2 alpha receptor in luteal cells of pseudopregnant mice.