Characteristics of the Stimulatory Effect of Kisspeptin-10 on the Secretion of Luteinizing Hormone, Follicle-Stimulating Hormone and Growth Hormone in Prepubertal Male and Female Cattle

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) and growth hormone (GH) in prepubertal male and female cattle. The experiments were performed from May to June using five male (4-6 months old) and five female (5-6 months old) Japanese Black calves. A single intravenous (iv) injection of Kp10 (5 mu g/kg body weight (b.w.): 3.85 nmol/ kg b.w.) significantly stimulated the release of LH and FSH in male and female calves (P<0.05). A single intramuscular injection of Kp10 (5 mu g/kg b.w.) also significantly stimulated the release of LH and FSH in male calves (P<0.05), though the response was smaller than that to the iv injection. The injection of Kp10 did not alter the basal plasma concentration of GH in male or female calves. The area under the curve (AUC) of both LH and FSH for a 120-min period after the iv injection of Kp10 was significantly greater in the males than females (P<0.05). These results show that Kp10 can stimulate the release of LH and FSH in calves of both sexes and that the response to the peptide is greater in males at this age. They also show that Kp10 has no effect on the release of GH in male and female calves and that the LH- and FSH-releasing effect of Kp10 is greater after an iv injection than after an im injection in calves.