Synergy of L-arginine and growth hormone (GH)-releasing peptide-2 on GH release: influence of gender. Am J Physiol Regulatory Integrative Comp Physiol 279: R1455-R1466

and growth hormone (GH)-releasing peptide-2 on GH re-lease: influence of gender. Am J Physiol Regulatory Integra-tive Comp Physiol 279: R1455–R1466, 2000.—We test the hypotheses that 1) growth hormone (GH)-releasing peptide-2 (G) synergizes with L-arginine (A), a compound putatively achieving selective somatostatin withdrawal and 2) gender modulates this synergy on GH secretion. To these ends, 18 young healthy volunteers (9 men and 9 early follicular phase women) each received separate morning intravenous infu-sions of saline (S) or A (30 g over 30 min) or G (1 mg/kg) or both, in randomly assigned order. Blood was sampled at 10-min intervals for later chemiluminescence assay of serum GH concentrations. Analysis of covariance revealed that the preinjection (basal) serum GH concentrations significantly determined secretagogue responsiveness and that sex (P