Follicle-stimulating hormone and luteinizing hormone regulate the synthesis mechanism of dihydrotestosterone in sheep granulosa cells

Steroid hormones and receptors play important roles in female reproduction, and their expression patterns affect follicular growth and development. To examine the expression of dihydrotestosterone (DHT) synthases (5 alpha-reductases (5 alpha-red1 and 5 alpha-red2)) and androgen receptor (AR) during follicular development, and the regulation of DHT signalling by follicle-stimulating hormone (FSH) and luteinizing hormone (LH), we have used enzyme-linked immunosorbent assays, quantitative real-time polymerase chain reaction, immunohistochemical staining and Western blotting to examine DHT synthesis in small (<= 2 mm), medium (2-5 mm) and large (>= 5 mm) sheep follicles. Expression of 5 alpha-red1, 5 alpha-red2 and AR was observed in ovine ovaries, and with the development of follicles, the expressions of 5 alpha-red1 and 5 alpha-red2 mRNA and protein increased, but the levels of AR mRNA, protein and DHT level decreased. In addition, granulosa cells were treated with FSH (0.01, 0.1 and 1 international unit (IU)/ml), LH (0.01, 0.1 and 1 IU/ml) and testosterone (T, 10(-7) M) to evaluate the effects of FSH and LH on DHT and oestradiol (E2) synthesis and 5 alpha-red1, 5 alpha-red2 and AR expression. We found that FSH and LH upregulated 5 alpha-red1 and 5 alpha-red2 in sheep granulosa cells, but downregulated the concentration of DHT and expression of AR. Meanwhile, FSH and LH significantly upregulated the expression of aromatase (P450arom) and secretion of E2. This result indicates that although FSH and LH promote the expression of 5 alpha-red1 and 5 alpha-red2, T is not transformed into DHT, but E2. This study reveals the reason why DHT concentration is downregulated in large follicles and lays a foundation for further exploring the synthesis mechanism of DHT during follicular development.