Changes in plasma concentrations of growth hormone and luteinizing hormone in ewes following central and peripheral treatment with kisspeptin
Kisspeptin (KP), a neuroendocrine regulator of gonadotropin releasing hormone, has been hypothesized as an integrator of nutrition and hormones critical to metabolism and regulation of reproduction. Recent evidence suggests growth hormone (GH) secretion may be influenced by KP. The objective of this study was to determine if the GH stimulatory effect of KP is due to actions on the hypothalamus or anterior pituitary gland in ewes. Adult ovariectomized ewes (n=8) were fitted with intracerebroventricular (ICV) cannula to facilitate central administration of experimental treatments. Ewes received one of eight treatments [four intravenously (IV) and four ICV]. Peripheral treatments [0 (Veh), 100, 200, or 1000 pmoles/kg body weight (BW) KP-10 (human KP 45-54; 4389-v, Peptide Institute, Inc., Osaka, Japan) in saline] were administered as a bolus via jugular cannula and ICV treatments [Veh, 50, 100, or 200 pmoles/kg BW KP-10] were administered via the ICV cannula. Blood samples were collected from a jugular cannula at -15, 0, 10, 20, 30, 45, 60, and 75 min relative to treatments. Experiments were repeated until all ewes received each treatment. Plasma GH and luteinizing hormone (LH) concentrations were determined by radioimmunoassay. Effects of treatment on plasma concentrations of LH and GH were tested using procedures for repeated measures (SAS Institute Inc., Cary, NC). The 200 and 1000 pmol/kg IV KP-10 increased (P < 0.05) plasma concentrations of LH. However, there was no effect of IV KP-10 on plasma GH. Conversely, 100 and 200 pmol/kg KP-10 administered ICV increased (P < 0.05) plasma GH concentrations. Maximum GH responses occurred 30 min following ICV KP-10 injection and were greater (P < 0.05) than both Veh and the 50 pg/ml KP-10 ICV. In addition to activating the gonadotropic axis, KP can activate the somatotropic axis in ruminants and present data support a central site of action.
Brian K. Whitlock, Joseph A. Daniel, Barbara P. Steele, and James L. Sartin. "Changes in plasma concentrations of growth hormone and luteinizing hormone in ewes following central and peripheral treatment with kisspeptin" 2010
Available at: http://works.bepress.com/brian_whitlock/39