Immunohistochemical determination of membrane and membrane-associated progesterone receptors in the ovine corpus luteum during early pregnancy

Aim: In this study, it was aimed to investigate the presence and expression profiles of membrane progesterone receptor alpha (mPRα), and membrane-associated progesterone receptor component 1 (PGRMC1) during the oestrus cycle and early pregnancy in ovine corpus luteum (CL). Material and Method: For this purpose, multiparous ewes were selected and randomly allotted into cyclic (n = 4 for per group) or pregnant (n = 4 for per group) groups. All of the ewes were scheduled to be slaughtered for predetermined days during the estrous cycle, early pregnancy. The CLs were collected from both cyclic and pregnant ewes on days 12 (C12 and P12), 16 (C16 and P16) and 22 (C22 and P22). Western blotting and Quantitative polymerase chain reaction were used to evaluate the expression profiles of PGRMC1 and mPRα while immunohistochemistry was used to define the spatial localization of PGRMC1 and mPRα in ovine CL. Data were then analyzed by one-way ANOVA and were considered statistically significant when P values were lower than 0.05. Results: PGRMC1 was found to be expressed in large, small luteal cells and endothelial cells in ovine CL. On the other side, mPRα was detected only in large and small luteal cells. The expression profile of PGRMC1 increased significantly in pregnant ewes CL, compared to cyclic days. While mPRα did not change during early pregnancy, it decreased significantly in CL only during the functional regression period (C16). Both protein and mRNA expression profiles of PGRMC1 and mPRα was similar. Conclusion: This is the first study that shown expression and localization of PGRMC1 and mPRα in ovine CL during the oestrus cycle and early pregnancy. The presence of mPRα and PGRMC1 in specific CL cell types and their significant changes in expression levels at protein and mRNA levels during early pregnancy and/or oestrus cycle clearly indicate that these receptors may have an important role in the establishment of pregnancy and luteolysis.