Na+/K+-ATPase: expression and regulation at the maternal-fetal interface during pregnancy in pigs

The establishment and maintenance of pregnancy require well-coordinated interactions between the endometrium and the conceptus involving cellular and secretory components. Na+/K+-ATPase, composed of alpha, beta, and Phe-X-Tyr-Asp (FXYD) subunits, plays important roles in maintaining Na+/K+ flux and mediating nutrient transport in the cell. Although the importance of Na+/K+-ATPase during pregnancy has been shown in some species, the expression, regulation, and function of Na+/K+-ATPase subunits at the maternal-conceptus interface remains poorly understood.

We obtained endometrial tissues during the estrous cycle and pregnancy, conceptus tissues during early pregnancy, and chorioallantoic tissues from mid to late pregnancy, and analyzed the expression of Na+/K+-ATPase subunits in pigs. The effects of steroid hormones, cytokines, and A23187, a calcium ionophore, on the expression of Na+/K+-ATPase subunits were examined in endometrial explant cultures.

Several Na+/K+-ATPase subunits in the endometrium changed dynamically during pregnancy, with some subunits having higher expression during early pregnancy than during the estrous cycle. Endometrial and chorionic epithelial cells were the primary sites of expression for Na+/K+-ATPase subunits. Conceptus-derived estrogen, interleukin-1β and/or interferon-γ, as well as A23187 all increased the expression of many subunits. Na+/K+-ATPase subunits were also expressed in conceptuses during early pregnancy and in chorioallantoic tissues between mid to term pregnancy.

Na+/K+-ATPase subunits expressed in endometrial, conceptus, and chorioallantoic tissues may play important roles in maintaining membrane potential and modulating nutrient transport in endometrial and conceptus tissues to ensure the successful establishment and maintenance of pregnancy in pigs.