Fas and Fas ligand messenger ribonucleic acid and protein expression in the rat corpus luteum during apoptosis-mediated luteolysis

Apoptosis has been found to occur during regression of the corpus luteum (C L) in many species. The Pas (APO-1/CD95) receptor, a transmembrane protein that induces apoptosis in the cell when bound to Fas ligand (FasL), may be involved. This study established and quantitated the presence and regulatio n of Pas receptor and Fast in the rat Ct. during pregnancy and postpartum. Using immunohistochemistry, Fast was localized in Ct. during pregnancy and postpartum. Fas was localized at Day 1 of pregnancy and at the time of lute olysis. Both Fas and Fast mRNA were found to be expressed throughout pregna ncy and postpartum using reverse transcription-polymerase chain reaction (R T-PCR). Relative quantitative RT-PCR established that expression of Fast mR NA increased significantly at Day 22 of pregnancy and decreased by Day 3 po stpartum. Spontaneous apoptosis of raf: Ct. placed in an in vitro culture m odel with serum-free medium was examined by analysis of extracted DNA using 3' end-labeling. Treatment with an anti-rat Fas monoclonal antibody demons trated a reduction in the occurrence of spontaneous apoptosis. These data s upport a role for Pas receptor and Fast in rat CL apoptosis during luteolys is.