Reproduction and beyond, kisspeptin in ruminants

Kisspeptin (Kp) is synthesized in the arcuate nucleus and preoptic area of the hypothalamus and is a regulator of gonadotropin releasing hormone in the hypothalamus. In addition, Kp may regulate additional functions such as increased neuropeptide Y gene expression and reduced proopiomelanocortin (POMC) gene expression in sheep. Other studies have found a role for Kp to release growth hormone (GH), prolactin and luteinizing hormone (LH) from cattle, rat and monkey pituitary cells. Intravenous injection of Kp stimulated release LH, GH, prolactin and follicle stimulating hormone in some experiments in cattle and sheep, but other studies have failed to find an effect of peripheral injection of Kp on GH release. Recent studies indicate that Kp can stimulate GH release after intracerebroventricular injection in sheep at doses that do not release GH after intravenous injection. These studies suggest that Kp may have a role in regulation of both reproduction and metabolism in sheep. Since GH plays a role in luteal development, it is tempting to speculate that the ability of Kp to release GH and LH is related to normal control of reproduction.