HIGH-DOSE INHALED ATRIAL-NATRIURETIC-PEPTIDE IS A BRONCHODILATOR IN ASTHMATIC SUBJECTS

Atrial natriuretic peptide (ANP) has been shown to be an effective bro nchodilator when given intravenously, but its efficacy by inhalation h as not been assessed. In the first part of the current study, six asth matic subjects, mean (SEM) forced expiratory volume in one second (FEV (1)) 2.09 (0.30) l, received 0.1 and 1 mg atrial natriuretic peptide b y inhalation, and in the second study five subjects, FEV(1) 1.92 (0.40 ) l, received 5 mg ANP by inhalation. ANP was given in a placebo-contr olled, double blind, randomized manner, with measurement of FEV(1) ove r the following 60 min. Nebulized salbutamol was given at 60 min as a measure of the maximal bronchodilator response attainable by conventio nal therapy. No significant bronchodilator effect was seen following t he 0.1 or 1 mg inhalation, although the latter produced a minimal tran sient elevation in peripheral atrial natriuretic peptide plasma levels . A bronchodilator effect was seen with the 5 mg dose, which produced Delta FEV(1) 0.42 (0.09) l compared to 0.93 (0.13) l subsequently prod uced by salbutamol. This effect peaked at 5 min and was no different f rom placebo from 10 min onwards. We conclude that atrial natriuretic p eptide may produce significant bronchodilation when given by inhalatio n in high doses, and speculate that substances which generate cyclic g uanosine monophosphate (cGMP) in airway smooth muscle warrant further investigation as potential bronchodilatory agents.