The Effect of New Growth Hormone-Releasing Peptide (KP102) on the Release of Growth Hormone in Goats

Abstract

The effects of KP102 (also named GHRP-2), a new growth hormone-releasing peptide, on the release of growth hormone (GH) were examined in female goats. The intravenous (iv) single injection of both 5μg (1.12μM) and 10μg (224μM)/kg BW of KP102 failed to stimulate significant GH release; however, the dose of 20μg (4.48μM)/kg BW of KP102 significantly (P<0.05) stimulated GH release. GH responses to a series of 5iv injections of KP102( 20μg/kg BW) at 2-h intervals increased plasma GH levels after each injection; however, the responses induced by KP102 were different from that by GH-releasing factor (GRF, 0.5μg (29.78nM)/kg BW). The GH responses after the injections of KP102 were a little delayed, and the elevated GH levels gradually decreased to the basal concentrations compared with GRF. Furthermore, small irregular GH peaks that were not observed in GRF appeared throughout the experiments. The GH responses to KP102 were decreased by repeated injections of KP102 as observed in GRF. The responses to plasma GH to a single iv injection of GRF (0.25μg (14.89nM) or 0.5μg/kg BW), KP102 (20μg/kg BW) or GRF (0.25 or 0.5μg/kg BW) plus KP102 (20μg/kg BW) were examined; however, signincant synergistic effects for GH release by both peptides were not observed. The present study shows that KP102 stimulates GH release in goats.