The effects of neuromedin S on the hypothalamic-pituitary-testicular axis in male pigs in vitro.

Evidence has shown that neuromedin S (NMS) and its receptor (NMU2R) are expressed in the hypothalamus, pituitary, and testis of pigs. To determine the potential mechanisms of NMS, we systematically investigated the direct effects of NMS on the hypothalamic-pituitary-testicular (HPT) axis of male pigs in vitro. We initially confirmed that NMU2R distributed in isolated hypothalamic cells, anterior pituitary cells and Leydig cells using immunocytochemistry. Subsequently we investigated the direct effects of NMS on hormone secretion from cells (anterior pituitary cells and Leydig cells) treated with different doses of NMS. The results showed that NMS increase the release of LH and FSH from anterior pituitary cells and testosterone from Leydig cells. NMS up-regulated the expression of NMU2R and GnRH mRNAs in hypothalamic cells, NMU2R, LH and FSH mRNAs in anterior pituitary cells, and NMU2R, STAR, P450 and 3β-HSD mRNAs and the expression of PCNA and Cyclin B1 protein in Leydig cells; moreover, it down-regulated the expression of GnIH mRNA in hypothalamic cells. Using immunofluorescence staining and confocal microscopy, we also demonstrated the colocalization of NMU2R and AR or GnIH in Leydig cells. These data in vitro indicated that NMS may regulate the release and/or synthesis of LH, FSH and testosterone at different levels of the reproductive axis through NMU2R, which provided novel evidence of the potential roles of NMS in regulation of pig reproduction.