Lack of effect of nitric oxide inhibition on bronchial tone and methacholine-induced bronchoconstriction in man.
The role of nitric oxide (NO) as a bronchodilator has been studied in humans with controversial results. The aim of the present study was to investigate the role of endogenous NO on bronchial tone by studying whether nitric oxide synthase (NOS) inhibition with NGnitro-L-arginine-methyl-ester (L-NAME) influences basal bronchial tone, or potentiates methacholine-induced bronchoconstriction. In a preliminary experiment in five subjects, a significant reduction in exhaled NO was found after delivering L-NAME (15 mg in saline) (from 3.9 +/- 1.2 to 2.4 +/- 1.1 nmol min-1, P < 0.05). In nine healthy non-smokers, specific airway conductance (SGAW), as a measure of airway calibre, was recorded after delivering, in a double-blind, controlled vs. placebo fashion, both nebulized L-NAME and saline, at baseline and after methacholine-induced bronchoconstriction. There was no significant difference between the baseline SGAW values before and after delivering L-NAME (0.264 +/- 0.04 and 0.267 +/- 0.05 cm H2O-1 s-1, respectively). After pre-treatment with L-NAME, SGAW values during methacholine-induced bronchoconstriction were not different in comparison to values obtained after saline inhalation. It is concluded that decreased endogenous NO does not influence bronchial tone in healthy people, nor does it modify methacholine-induced bronchoconstriction.
Maniscalco
M
M
Department of Respiratory Disease, University Federico II, Naples, Italy.
Sofia
M
M
Smith
A
A
Demoncheaux
E A
EA
Mormile
M
M
Faraone
S
S
Higenbottam
T
T
D000328:Adult; D000403:Airway Resistance / Q000187:drug effects*; D001944:Breath Tests; D016085:Bronchoconstrictor Agents; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D008297:Male; D016210:Methacholine Chloride; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology*; D009569:Nitric Oxide / Q000502:physiology*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors*
D016085:Bronchoconstrictor Agents; D016210:Methacholine Chloride; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase; D019331:NG-Nitroarginine Methyl Ester