The effect of inhaled ouabain on bronchomotor tone and histamine responsiveness in asthmatic patients.

We have studied the effect of inhaled ouabain on resting bronchomotor tone and histamine responsiveness in eight asthmatic patients in an attempt to clarify the role of Na/K ATPase in airway reactivity. Doses ranged from 50 micrograms to 5000 micrograms and were given in a placebo controlled, double blind manner. Baseline FEV1 was recorded prior to inhalation and at intervals up to 30 min thereafter. At 30 min, a histamine provocation test was performed and results expressed as that concentration producing a 20% fall in FEV1. Maximum fall in FEV1 was not significantly different between placebo or any dose of ouabain, ranging from 4.3%-8.2% (p greater than 0.06) nor was histamine reactivity altered significantly (geometric mean range 0.17 mg-0.29 mg [p greater than 0.2]). Unlike animal studies therefore, we have been unable to demonstrate any effect of Na/K ATPase inhibition on airway reactivity in vivo.