Cell-specific immuno-localization of progesterone receptor alpha in the rabbit ovary during pregnancy and after parturition

Progesterone receptor alpha (PRA) has a central coordinator role in the ovarian functions in mammals. The aim of this study was to investigate the immunolocalization of PRA in the rabbit ovary during pregnancy and after parturition. The rabbit ovary during pregnancy and after parturition had moderate cytoplasmic and moderate to intense nuclear PRA immunostaining in the ovarian surface epithelial cells, stromal cells and interstitial gland cells. The PRA was also present in granulosa cells and theca interna cells of the growing, small antral and mature Graafian follicles. Theca interna cells of the atretic antral follicle in addition to endothelial and fibroblast cells had PRA immunoreactivity. The PRA were also observed in the theca externa smooth muscle-like cells of the growing and antral follicles and in the telocytes. In the present study, the corpora haemorrhagica and early developing corpora lutea had, slight cytoplasmic and nuclear PRA immunostaining in the large lutein and small lutein cells. The endothelial cells of the corpora haemorrhagica and corpora lutea had an intense nuclear PRA immune signal. The corpora lutea at an advanced stage of development had moderate cytoplasmic and nuclear PRA immunostaining in the large lutein cells and intense nuclear PRA immunostaining in the small lutein cells. The regressed corpora lutea did not have PRA immunostaining in the apoptotic large lutein cells and moderate cytoplasmic and intense nuclear PRA immunostaining in the small lutein cells.