Expression of 11beta-hydroxysteroid dehydrogenases in bovine follicle and corpus luteum

Abstract

In glucocorticoid target organs, local concentrations of active glucocorticoid are determined by the relative expression of two 11beta-hydroxysteroid dehydrogenases (HSDs): bi-directional 11beta-HSD type1 (11HSD1) that mainly activates cortisone to cortisol, and dehydrogenase 11beta-HSD type2 (11HSD2) that inactivates cortisol to cortisone. In this study, we examined the expression of mRNA encoding these two 11beta-HSDs in bovine granulosa cells harvested from preovulatory follicles and corpora lutea (CL). Ovaries were obtained from Holstein cows at a local slaughterhouse. Follicles larger than 10 mm in diameter and CL were dissected and follicular fluid and granulosa cells were taken. Corpora lutea were weighed and their stages were morphologically assessed (stage I, days 1-4; stage II, days 5-10; stage III, days 11-17; stage IV, days 8-20). Follicles were classified into four groups according to their hormonal status (oestradiol (E(2)): progesterone (P(4))>1: oestrogen active; E(2):P(4)<1: oestrogen inactive) and stage of the oestrous cycle (luteal or follicular phase). Total RNA was extracted with phenol-chloroform and subjected to a semi-quantitative RT-PCR for 11HSD1, 11HSD2 and beta-actin. Concentrations of steroids in follicular fluid were determined by an enzyme immunoassay. In granulosa cells, only 11HSD1 mRNA was detected. There was a negative correlation between the expression of 11HSD1 and the concentration of cortisol in follicular fluid (P<0.05), indicating 11HSD1 may act as a dehydrogenase in the bovine follicle. Both types of 11beta-HSDs were expressed in CL. The levels of mRNA for both isozymes were high in stage I and II, and were decreased in stage III CL. In stage IV CL, the expression of 11HSD2 but not 11HSD1 mRNA increased. These results indicate that the bovine granulosa cells and CL express 11HSD1 and 11HSD2, and they may play an important physiological role in the bovine ovary through modulating the local glucocorticoid environment.