Purinergic system molecules: expression and regulation of enzymes, transporters, and adenosine triphosphate receptors and the role of adenosine triphosphate at the maternal–conceptus interface in pigs

The purinergic system is composed of purine nucleotides, enzymes, transporters, and receptors and is involved in a variety of physiological processes in the body, including development, metabolism, immunity, tumorigenesis, and reproduction. The importance of the purinergic system for embryo implantation in the endometrium and in pathophysiological conditions has been shown in some species. However, the expression, regulation, and function of purinergic system molecules at the maternal-conceptus interface in pigs is not fully understood. Therefore, we determined the expression of purinergic system molecules in the endometrium during the estrous cycle and pregnancy and in the conceptus and chorioallantoic tissues during pregnancy in pigs. The expression of many purinergic system molecules in the endometrium changed dynamically during pregnancy, with the expression of several components in the endometrium greater on day 15 of pregnancy than day 15 of the estrous cycle, and it was regulated by conceptus-derived interleukin-1beta and interferon-gamma. Purinergic system molecules were also expressed in conceptuses during early pregnancy and in chorioallantoic tissues during mid- to term pregnancy. Furthermore, adenosine triphosphate, a major purinergic signaling molecule, increased migration of endometrial epithelial and conceptus trophectoderm cells, the expression of prostaglandin synthetic enzymes, and the secretion of prostaglandin F2alpha in endometrial epithelial cells in vitro. These data suggest that the purinergic system molecules expressed in the endometrium, conceptus, and chorioallantoic tissues might play an important role in the establishment and maintenance of pregnancy by regulating various cellular functions at the maternal-conceptus interface in pigs.