Effect of kisspeptin antagonist on goat in vitro Leydig cell steroidogenesis

Kisspeptin is the protein product of Kiss1 gene. In contrast to its fundamental role as GnRH Secretagogue and puberty initiation, its functions in extrahypothalmic tissues such as the testes remain unknown. The objective of this study was to investigate the potential local role of kisspeptin in the Leydig cell culture in goats. Five male Shiba goats were castrated to isolate Leydig cells from the testes. The isolated Leydig cells were then purified and cultured with different concentration of kisspeptin antagonist (0, 5, and 10 nmol; 0KPA, 5KPA, and 10KPA; respectively). After 12 h, 20 IU of hCG was added to some wells (0KPA + hCG, 5KPA + hCG, and 10KPA + hCG; respectively); other wells did not receive hCG (0KPA + Con, 5KPA + Con, and 10KPA + Con; respectively). Media of Leydig cell culture was harvested at 2, 6, 12, and 24 h after addition of hCG for testosterone (T) and estradiol (E2) assays. The contents of some non KPA treated wells (0KPA + Con and 0KPA + hCG wells) were collected and stored at -80 ^OC for further identification the expression of mRNA encoding Kiss1 and its receptor (GPR54) using real time PCR. Results revealed high expressions of Kiss1/GPR54 mRNAs in the hCG treated (0KPA + hCG) wells compared to non-hCG treated ones (0KPA + Con). KPA significantly reduced the basal T production at 6 h incubation as well as hCG-induced T production in 2, 6, and 24 h incubation. Basal E2 concentrations were significantly lower in the KPA treated wells at 6, and 24 h likewise, KPA significantly attenuated induced E2 production at 12 h compared with its values in non KPA treated wells. In conclusion, kisspeptin antagonist significantly attenuated both basal and hCG-activated T and E2 production by purified Leydig cells in goats. Therefore, involvement of kisspeptin in the steroidogenic capability of Leydig cells is possible in goats.