Arginine Potentiates the Ghrh‐ but Not the Pyridostigmine‐induced Gh Secretion in Normal Short Children. Further Evidence for a Somatostatin Suppressing Effect of Arginine

Abstract

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 microgram/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/l). The combined administration of ARG and GHRH led to GH levels (101 +/- 15.2 mU/l) higher than those observed after GHRH (P less than 0.025) or ARG alone (P less than 0.001) and overlapping with those recorded after combined PD and GHRH administration (111 +/- 22.4 mU/l). 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/l, respectively) or in combination (33.8 +/- 5.4 mU/l). 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.

Unequal impact of age, percentage body fat, and serum testosterone concentrations on the somatotrophic, IGF-I, and IGF-binding protein responses to a three-day intravenous growth hormone-releasing hormone pulsatile infusion in men

“…However, an interpretation of a partial Table 1. or non-exclusive diminution in (endogenous) GHRH action is consistent with reported near-normalization of blunted GH secretion in older men administered GHRH intermittently or continuously over 12 to 14 days (10). On the other hand, GH secretion failed to rise in obese or older subjects treated once daily with GHRH for 15 days (24,25). Once daily GHRH treatment for 6 weeks also did not normalize serum IGF-I or IGFBP-3 concentrations in older men (26).…”

Plasma growth hormone (GH), insulin and amino acid responses to arginine with or without aspartic acid in pigs. Effect of the dose

“…This is believed to be due to their somatostatinergic hypertone [35]. ARG-induced GH release is probably mediated by a decrease in the somatostatinergic tone as demonstrated indirectly by the use of cholinesterase inhibitors in man [1,18,20] and pigs [10].…”

Is there an undiscovered neurocircuit for regulating GH secretion? -Pitfalls of GHRP-2 and ITT as GH provocative tests-

“…However, the low response to evoke GH release by GHRP-2 may not be explained by enhanced SRIF tone, since GHRPs act as potent functional SRIF antagonists [38], and the GH-releasing activities of GHRPs are resistant to inhibition by SRIF [39]. With this reference, arginine test was not performed in this subject because that arginine lording has a similar mechanism underling GH secretion with inhibition of SRIF secretion [38,39] and with enhancing activity of GHRH [40] as GHRP-2 loading.…”