Prostaglandin E Receptors In Porcine Uterus During Estrous Cycle And Early Pregnancy

Prostaglandin E2 (PGE2) exerts a wide variety of physiological actions in mammalian reproductioa PGE2 receptors are classified into four subtypes, EP1, EP2, EP3, and EP4. The expression and regulation of PGE2 receptor genes in porcine uterus during the estrous cycle and early pregnancy are still unknown. This study was to examine the expression of EP2, EP3, and EP4 in porcine uterus during the estrous cycle and early pregnancy by immunohistochemistry.The immunostaining of EP2, EP3 and EP4 was mainly located in the luminal epithelium and glandular epithelium, and was stronger on days 0 and 6 of the estrous cycle. A comparatively strong immunostaining of EP2, EP3, and EP4 was detected in the luminal epithelium and glandular epithelium on days 3 and 5 of pregnancy, while the immunostaining was remarkably reduced from day 7 of pregnancy. The immunostaining then increased on day 11 of pregnancy. However, all these receptors were not detectable on days 12-14 of pregnancy, and the immunostaining of EP2, EP3, and EP4 was gradually increased during the postimplantation period of pregnancy. A strong immunostaining of EP2 and EP3 was observed in maternal uterine luminal epithelium and glandular epithelium and the apical aspects of the apposing conceptus trophectoderm on days 25-27 of pregnancy.Strong level of EP3 immunostaining and moderate level of EP4 immunostaining were detected in endometrial vascular endothelial cells on days 0 and 6 of the estrous cycle. The immunostaining of EP3 in vascular endothelial cells was strong on days 3, 5 and 27 of pregnancy. A moderate level of EP4 immunostaining was observed in vascular endothelial cells from day 14 of pregnancy. There was detectable EP3 and EP4 immunostaining in the myometrium on days 0 and 6 of the estrous cycle, and days 3 and 5 of pregnancy.In conclusion, PGE2 action in porcine uterus may be mediated by EP2, EP3 and EP4 receptors. The expressions of EP2, EP3 and EP4 genes in porcine uterus may be related to the epithelial cell proliferation, gland development, vascular endothelial cell proliferation, urerine contractions, establishment of uterine receptivity and formation of epitheliochorial placenta during the estrous cycle and early pregnancy.