Interaction of salbutamol with pyridostigmine and arginine on both basal and GHRH-stimulated GH secretion in humans.
OBJECTIVE
It is well known that acetylcholine and arginine stimulate GH secretion while activation of beta-adrenergic receptors inhibits GH secretion in man. We aimed therefore to ascertain whether or not the inhibitory influence of beta-adrenergic receptors on GH secretion would over-ride the stimulatory one of acetylcholine and arginine.


METHODS
We studied the interaction of salbutamol, a beta 2-adrenergic agonist (SAL, 0.08 mg/kg orally) with pyridostigmine, a cholinesterase inhibitor (PD, 120 mg orally), or arginine (0.5 g/kg i.v.) on both basal and GHRH (1 microgram/kg i.v.)-stimulated GH secretion.


METHODS
Fourteen healthy male volunteers, aged 20-35 years, were studied.


METHODS
Serum GH was measured in duplicate by immunoradiometric assay.


RESULTS
In study A, SAL inhibited the GH response both to GHRH (P < 0.01) and ARG (P < 0.002). ARG enhanced the GHRH-induced GH rise (P < 0.01) but its effect was abolished (P < 0.02) by SAL pretreatment. In study B, SAL inhibited the GH response both to GHRH (P < 0.01) and PD (P < 0.02). PD enhanced the GH response to GHRH (P < 0.001) but its effect was abolished (P < 0.05) by SAL pretreatment. In both studies, the GH response to GHRH alone was similar to that to the neurohormone when combined with ARG + SAL or PD + SAL.


CONCLUSIONS
Our results show that beta 2-adrenergic activation by salbutamol is able to inhibit not only the GH rise induced by GHRH, arginine and pyridostigmine, but even the potentiating effect of both arginine and pyridostigmine on the GH response to GHRH. They indicate that catecholamines, acetylcholine and arginine play a major role in GH secretion having opposite influences aimed to balance the function of the hypothalamus-GH-IGF-I axis in man.
Department of Clinical Pathophysiology, University of Turin, Italy.
E
E
Ghigo
E
E
Arvat
L
L
Gianotti
J
J
Ramunni
M
M
Maccario
F
F
Camanni
D000328:Adult; D000420:Albuterol / Q000494:pharmacology*; D001120:Arginine / Q000494:pharmacology*; D003864:Depression, Chemical; D004357:Drug Synergism; D007987:Gonadotropin-Releasing Hormone / Q000494:pharmacology*; D013006:Growth Hormone / Q000097:blood / Q000378:metabolism*; D006801:Humans; D015592:Immunoradiometric Assay; D008297:Male; D011729:Pyridostigmine Bromide / Q000494:pharmacology*; D011897:Random Allocation
D007987:Gonadotropin-Releasing Hormone; D013006:Growth Hormone; D001120:Arginine; D011729:Pyridostigmine Bromide; D000420:Albuterol