Expression of 17β-hydroxysteroid dehydrogenase and the effects of LH, FSH and prolactin on oestrone and 17β-oestradiol secretion in the endometrium of pigs during early pregnancy and the oestrous cycle

Abstract

The endometrium of pregnant and cyclic pigs is a source of oestrone (E1) and 17β-oestradiol (E2). However, the roles of LH, FSH and prolactin (PRL) as regulators of endometrial steroidogenesis, and the presence of 17β-hydroxysteroid dehydrogenase (17β-HSD) in the porcine endometrium, remain unknown. Therefore, in the present study we examined 17β-HSD expression and the effects of LH, FSH and PRL on E1 and E2 release in vitro in endometrial explants harvested from gravid pigs on Days 10–11 (embryo migration within the uterus), 12–13 (maternal recognition of pregnancy) and 15–16 (beginning of implantation) and compared them with results obtained in non-gravid pigs. The results show that: (1) endometrial 17β-HSD activity was decreased on Days 15–16 in pregnant and cyclic pigs compared with the preceding days; (2) LH, FSH and PRL increased endometrial E1 secretion on Days 10–11 and 15–16 of pregnancy and on Days 12–13 and 15–16 of the oestrous cycle; and (3) LH, FSH and PRL increased endometrial E2 secretion on Days 15–16 of pregnancy and during the days studied in the oestrous cycle. In conclusion, data suggest that LH, FSH and PRL affect endometrial secretion of estrogens in pigs.