Abstract
Negative feedback on GH responses to GH-releasing hormone (GHRH) and GH-releasing peptides (GHRPs) has been reported and this action has been suggested to act through an increase in somatostatin. To determine whether the acute administration of porcine GH (pGH) inhibits GH responsiveness to GHRP-2 and GHRH in swine, swine were intravenously administered with pGH (5 µg/kg BW) or placebo followed 180 min later by a second intravenous administration of saline, GHRP-2 (30 µg/kg BW), GHRH (1 µg/kg BW) and a combination of GHRP-2 and GHRH. Plasma GH concentration was measured by radioimmunoassay. Administration of pGH caused a significant increase in GH area under curve and GH peak concentrations (p<0.001) over placebo-treated group. Plasma GH concentrations peaked at 15 min and returned to baseline level within 90 min. Pretreatment of pGH abolished (p<0.01) GH response to GHRH and attenuated (p<0.05) GH response to GHRP-2 and GHRH combined, without affecting GH response to GHRP-2. These results demonstrate that negative feedback action on GH releasing effect of GHRH occurs in swine, and that GHRP-2 has ability to interact in this action. (Asian-Aust. J. Anim. Sci. 2003. Vol 16, No. 8 : 1188-1192)
Highlights
Growth hormone regulates its own secretion by a feedback mechanism operating both on the central nervous system and the pituitary (Muller et al, 1991)
Pretreatment of porcine GH (pGH) abolished (p
We have investigated the effect of acute exogenous porcine GH administration on GH
Summary
Growth hormone regulates its own secretion by a feedback mechanism operating both on the central nervous system and the pituitary (Muller et al, 1991). Difference in means of GH peak concentrations and GH AUCs after administration of saline, GHRH, GHRP-2, and GHRP-2 and GHRH combined within and between groups of swine were analyzed by student’s t-test and paired t-test, respectively.
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