Seasonal modulation of progesterone receptor, PCNA, and enzyme activity in buffalo uterus: implications for endometrial growth during oestrous.

Buffalo reproduction is influenced by seasonal variations. This study examined the key parameters affecting the uterine endometrial histoarchitecture during the follicular and luteal phases of the oestrous cycle across summer and winter. The expression of progesterone receptor (PR) and proliferating cell nuclear antigen (PCNA), essential indicators for endometrial cell proliferation and differentiation, was examined. The uterine alkaline phosphatase (AKPase) and succinic dehydrogenase (SDH) activity demonstrated active protein transport and DNA turnover within the nucleus, reflecting a cellular functional state. Twenty-four (N = 24) samples were taken from healthy adults (2-6 years) cyclic nonpregnant Murrah buffalo. The samples were grouped into two categories (summer and winter) based on the season of collection, where N = 12. For each season, the samples were sub-grouped into two (N = 6), according to the cyclic phase of the animal which was determined by gross macroscopic observation of functional CL on the surface of the ovary. Immunohistochemical staining for PR and PCNA, histoenzymatic staining for AKPase and SDH, was performed on uterine samples. The immunostaining intensity was quantified by measuring the optical density (OD) value of the antigen-antibody reaction and by calculating the percentage of immunopositive cells. Histoenzymic localization of AKPase and SDH of the uterine samples were done. The findings indicated that the immunoreactivity for PR and PCNA and the histoenzymatic localisation of AKPase and SDH were more evident during the luteal phase than in the follicular phase. Nonetheless, these factors declined throughout the summer compared to the winter. The seasonal declines indicate that diminished endometrial function adversely affects buffalo reproduction, potentially leading to summer sterility.