Regulation of 11β-hydroxysteroid dehydrogenase isoforms and glucocorticoid receptor gene expression in the rat uterus

Glucocorticoids are known to have diverse effects on the uterus, generally believed to be mediated by the glucocorticoid receptor (GR). To date, two isoforms of the enzyme 11 beta-hydroxysteroid dehydrogenase (11 beta HSD) have been identified, namely 11 beta HSD1 and 11 beta HSD2, which interconvert active and inactive glucocorticoids and regulate local levels of hormones available to the GR in target tissues. The aim of the present study was to examine the uterine expression of 11 beta HSD and GR mRNA. The interplay of these parameters is probably an important factor in determining actions of glucocorticoids on the uterus. Using Northern analysis we investigated the uterine expression of 11 beta HSD1, 11 beta HSD2 and GR mRNA in relation to serum levels of sex steroid hormones and uterine progesterone receptor mRNA expression in an animal model. Immature female rats were treated with 10 IU pregnant mare serum gonadotrophin (PMSG) followed by 10 IU human chorionic gonadotrophin (hCG) 48 h afterwards, and then killed at 0, 3, 6, 9, 12 and 24 h and 5 days after the hCG injection. Expression of both 11 beta HSD1 and 11 beta HSD2 mRNA in total uterine RNA was found to be: up-regulated by more than 50% at 48 h after PMSG injection when oestradiol levels were also high. Following hCG treatment the expression of 11 beta HSD1 and 11 beta HSD2 further increased to reach maximal levels at 24 and 12 h respectively. GR mRNA expression was down-regulated by more than 50% by PMSG but gradually recovered after hCG injection. The results show that mRNA expression of 11 beta HSD1, 11 beta HSD2 and GR in the uterus is developmentally regulated, suggesting that these key determinants of glucocorticoid action may play an important role in uterine function.