Synergy of L-arginine and growth hormone (GH)-releasing peptide (GHRP-2) stimulation of GH in men and women: Modulation by exercise

UNCG Author/Contributor (non-UNCG co-authors, if there are any, appear on document)
Laurie Wideman, Safrit-Ennis Distinguished Professor (Creator)
The University of North Carolina at Greensboro (UNCG )
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Abstract: We investigated the ability of exercise, a multipathway, potent, physiological stimulus for GH release, to alter the synergistic interaction of l-arginine (A) and GH-related peptide (GHRP)-2 (G) observed at rest and the ability of gender to further modulate this putative interaction. Subjects (9 men and 9 early follicular phase women) completed 30 min of constant load aerobic exercise in combination with intravenous infusions of saline (S), A (30 g over 30 min), G (1 µg/kg bolus), or both (AG) in separate study sessions in randomly assigned order. Measures of GH release were logarithmically transformed for statistical analysis. Similar to rest, exercise maintained the rank order (AG > G > A > S) of effective stimulation of GH release for the key response measures in men or women, a gender disparity in the time to reach the maximal serum GH concentration, the calculated endogenous GH half-life, and the observed effect of preinfusion (basal) serum GH concentrations on determining secretagogue responsiveness. Exercise potentiated the individual stimulatory actions of A and G, while blunting the relative magnitude of the synergistic (supra-additive) interaction observed at rest. We infer from the present data that 1) exercise is likely to induce release of both GHRH and somatostatin, 2)l-arginine may facilitate the effect of exercise by limiting somatostatin release, 3) GHRP-2 could further enhance the stimulatory impact of exercise by opposing central actions of somatostatin and/or heightening endogenous GHRH release, and4) gender strongly controls the relative but not absolute magnitude of A/G synergy both at rest and after exercise.

Additional Information

AJP: Regulatory, Integrative and Comparative Physiology 279: R1467-R1477
Language: English
Date: 2000
male, female, pituitary, somatotropin, regulation, endocrine

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