Kisspeptin-10 stimulates the secretion of growth hormone and prolactin directly from cultured bovine anterior pituitary cells

Kisspeptins are peptide hormones encoded by the KiSS-1 gene, and act as the principal positive regulator of the reproductive axis by directly stimulating gonadotropin-releasing hormone (GnRH) neuron activity. We recently observed that kisspeptin-10 (the minimal kisspeptin sequence necessary for receptor activation) also has a direct stimulating effect on luteinizing hormone (LH) secretion in bovine anterior pituitary (AP) cells. In the present study, we evaluated the direct effect of kisspeptin-10 on the secretion of other pituitary hormones, growth hormone (GH) and prolactin (PRL), from bovine AP cells. The AP cells, which were prepared from 1- or 8-month-old male calves, were incubated for 2h with the peptides. Kisspeptin-10 at 100nM (P <0.05), 1000nM (P <0.01) and 10,000nM (P <0.01), but not at 10nM, significantly stimulated GH secretion from the AP cells of 1-month-old calves, while in 8-month-old calves it was significantly (P <0.05) stimulated at 1000nM (P <0.01) and 10,000nM (P <0.01), but not at 10nM and 100nM. The response of GH to 100nM (P <0.01), 1000nM (P <0.05) and 10,000nM (P <0.01) kisspeptin-10 in the AP cells of 1-month-old calves was significantly greater than in those of 8-month-old calves. All tested doses of kisspeptin-10 had no effect on PRL secretion from AP cells of 1-month-old calves. However, 1000nM (P <0.05) and 10,000nM (P <0.01), but not lower concentrations, of kisspeptin-10 significantly stimulated PRL secretion from the AP cells of 8-month-old calves. The present study is, as far as we know, the first to examine the direct actions of kisspeptin on the secretion of GH and PRL from the bovine pituitary gland. Further studies are necessary to evaluate the importance of multiple actions of kisspeptin on the pituitary of various animals in vivo.