Characteristics of stimulation of gonadotropin secretion by kisspeptin-10 in female goats.

The aims of the present study were to clarify the effect of kisspeptin-10 (Kp10) on the secretion of luteinizing hormone (LH), follicle stimulating hormone (FSH), growth hormone (GH) and prolactin (PRL) in goats, and compare the characteristics of any response with those of the response to gonadotropin-releasing hormone (GnRH). The experiments were performed using four female goats (4-5 years old) in the luteal phase of estrous cycle. A single intravenous (i.v.) injection of 1, 5 and 10 microg/kg b.w. (0.77, 3.85 and 7.69 nmol/kg b.w.) of Kp10 stimulated the release of LH. Maximum values were observed 20-30 min after the injection. On the other hand, Kp10 did not alter plasma GH and PRL concentrations significantly. Three consecutive i.v. injections of Kp10 (5 microg/kg b.w.) or GnRH (5 microg/kg b.w.: 4.23 nmol/kg b.w.) at 2-h intervals increased both plasma LH and FSH levels after each injection (P<0.05); however, the responses to Kp10 were different from a similar level of GnRH. The rate of decrease in LH and FSH levels following the peak was attenuated in Kp10-treated compared to GnRH-treated animals. These results show that Kp10 can stimulate the release of LH and FSH but not GH and PRL in female goats and suggest that the LH- and FSH-releasing effect of the i.v. injection of Kp10 is less potent than that of GnRH.