ARGININE POTENTIATES THE GHRH- BUT NOT THE PYRIDOSTIGMINE-INDUCED GH SECRETION IN NORMAL SHORT CHILDREN - FURTHER EVIDENCE FOR A SOMATOSTATIN SUPPRESSING EFFECT OF ARGININE

To investigate the mechanism underlying the GH‐releasing effect of arginine (ARG), we studied the interactions of ARG (0.5 g/kg infused i. v. over 30 min) with GHRH (1 μg/kg i. v.) and with pyridostigmine (PD, 60 mg orally) on GH secretion in 15 children and adolescents with familial short stature (5.1‐15.4 years). In a group of eight subjects ARG induced a GH increase not statistically different to that observed after GHRH (peak, mean±SEM: 38.0±10.4 vs 64.0±14.4 mU/1). The combined administration of ARG and GHRH led to GH levels (101±15.2 mU/1) higher than those observed after GHRH (P < 0.025) or ARG alone (P < 0.001) and overlapping with those recorded after combined PD and GHRH administration (111±22.4 mU/1). In the other seven subjects, ARG and PD administration induced a similar GH response either when administered alone (25.2±13.6 and 27.8±4.0 mU/1, respectively) or in combination (33.8±5.4 mU/1). In conclusion, our results show that in children ARG administration potentiates GHRH‐ but not PD‐induced GH increase. These findings agree with the hypothesis that the GH‐releasing effect of both ARG and PD is mediated via the same mechanism, namely, by suppression of endogeneous somatostatin release. Combined administration of either ARG or PD with GHRH has a similar striking GH‐releasing effect which is clearly higher than that of GHRH alone. Copyright © 1990, Wiley Blackwell. All rights reserved