Kisspeptin-1 directly stimulates LH and GH secretion from goldfish pituitary cells in a Ca(2+)-dependent manner

It has been established that kisspeptin regulates reproduction via stimulation of hypothalamic gonadotropin-releasing hormone (GnRH) secretion, which then induces pituitary luteinizing hormone (LH) release. Kisspeptin also directly stimulates pituitary hormone release in some mammals. However, in goldfish, whether kisspeptin directly affects pituitary hormone release is controversial. In this study, synthetic goldfish kisspeptin-1((1-10)) (gKiss1) enhances LH and growth hormone (GH) release from primary cultures of goldfish pituitary cells in column perifusion. gKiss1 stimulation of LH and GH secretion were still manifested in the presence of the two native goldfish GnRHs, salmon (s)GnRH (goldfish GnRH-3) and chicken (c)GnRH-II (goldfish GnRH-2), but were attenuated by two voltage-sensitive calcium channel blockers, verapamil and nifedipine. gKiss-induced increases in intracellular Ca(2+) in Fura-2AM pre-loaded goldfish pars distalis cells were also inhibited by nifedipine. These results indicate that, in goldfish, (1) direct gKiss1 actions on pituitary LH and GH secretion exist, (2) these actions are independent of GnRH and (3) they involve Ca(2+) signalling.