Assessment of progesterone synthesis and its regulation role on dihydrotestosterone secretion in sheep epididymis

Progesterone (P4) is an anti-androgen compound whose role in sperm maturation and functionality remains unclear in sheep. Here, we aimed to investigate the regulation mechanism of P4 on the epididymal secretion of dihydrotestosterone (DHT). To this end, we performed enzyme-linked immunosorbent assays, immunohistochemical staining, western blotting, and quantitative real-time polymerase chain reaction to detect P4 concentration as well as StAR, P450scc, and 3 beta-HSD expression in sheep epididymis. Besides, cauda epithelial cells were cultured at different concentrations of P4 (10-9-10-5 g ml 1) as well as with or without the P4 receptor (PGR) inhibitor RU486 (10-7 M) or the PI3K-AKT inhibitor LY294006 (10-7 M) to explore the effect of P4 on DHT secretion and the underlying regulatory mechanism. The results showed that the caput, corpus, and cauda of sheep epididymis could synthesize P4 but had different synthesis ability. The PGR expression levels were the highest in the cauda, followed by the corpus. In vitro cell culture showed that P4 inhibition of DHT secretion and 5 alpha-reductase 1 and 2 expression in epididymal epithelial cells could be moderately mitigated by RU486 but not by LY294002. Our results indicated that the paracrine and autocrine P4 could affect the secretion of DHT in epididymal cells through PGR. Overall, this study provides new data regarding the involvement of P4 in sperm maturation and functionality in sheep.

Automated summary

The study investigated the regulatory mechanism of progesterone on the secretion of dihydrotestosterone in sheep epididymis, revealing different synthesis abilities of P4 in different parts of the epididymis and higher PGR expression levels in the cauda. In vitro cell culture experiments showed that inhibition of DHT secretion and 5 alpha-reductase 1 and 2 expression by P4 could be partially mitigated by RU486.