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. However, peripheral administration, as well as central administration, of kisspeptin stimulates luteinizing hormone (LH) secretion in some mammalian species. In order to evaluate the direct effects of kisspeptin-10 (the minimal kisspeptin sequence necessary for receptor activation) on LH secretion from bovine and porcine anterior pituitary (AP) cells, LH-releasing effects of kisspeptin-10 on AP cells were compared with GnRH in vitro. The AP cells were prepared from I-month-old intact male calves, 8-month-old castrated male calves, or 6-month-old barrows, and then the cells were incubated for 2 It with the peptides. The 1000 nM and 10,000 nM, but not lower concentrations, of kisspeptin-10 significantly stimulated LH secretion from the bovine A-P cells (P < 0.05). The 100nM and MOW, but not lower concentrations, of kisspeptin-10 significantly stimulated LH secretion from porcine AP cells (P < 0.05). As 10nM of GnRH strongly stimulated LH secretion from all AP cells tested in this study, the present results suggest that kisspeptin-10 has a direct, but weak, stimulating effect on LH secretion in bovine and porcine AP cells. The present study is the first to examine the direct actions of kisspeptin on the bovine and porcine pituitary gland as far as we know. Kisspeptin might have other actions on the pituitary because the pituitary has multiple roles. (c) 2007 Elsevier B.V. All rights reserved.
