Action of kisspeptin on in vitro gonadotropin release in the European sea bass (Dicentrarchus labrax)

Resumen del trabajo presentado en el 9º Congreso de la Asociación Ibérica de Endocrinología Comparada, celebrado en Barcelona (España), los días 13 y 14 de julio de 2013Kisspeptins are key players in the neuroendocrine control of puberty and other reproductive processes in mammals. It has been suggested that the effect of kisspeptins occurs exclusively at the level of hypotalamic GnRH secretion, since the stimulatory effect of kisspeptin on gonadotropin release is blocked by a GnRH antagonist. On the other hand, several studies have demonstrated that the KiSS/GPR54 system is expressed by the gonadotrops, but in vitro studies assessing the direct stimulatory effects of kisspeptin on gonadotropin secretion in the pituitary have given conflicting results. In this study, we aimed at investigating the direct effect of sea bass kiss1 and kiss2 on the pituitary. The highly active peptides kiss1-15 and kiss2-12 were used to stimulate dispersed sea bass pituitary cells obtained from mature males. In the presence of kiss2-12, a peak of LH release was observed after 8h of incubation, while the same concentration of this peptide induced a significant release of FSH in 4h. On the other hand, kiss1-15 had no effect on LH or FSH release. These results were different depending on the hormonal (GnRH or sexual steroids) milieu of the cells. Thus, kiss2-12 had a synergic effect with GnRH on LH release. In the presence of sexual steroids (estradiol and testosterone) the stimulatory effect of kiss2-12 on LH and FSH release was inhibited. In conclusion, our results provide unequivocal evidence that kisspeptin exert direct pituitary effects in spermiating male sea bass and suggests a possible autocrine/paracrine mode of action.Supported by the EU LIFECYCLE (FP7-222719-1) and the GV (REPROBASS; PROMETEO/2010/003)