Increased in vitro histamine responses in human small airways smooth muscle from patients with chronic obstructive pulmonary disease.

We tested the hypothesis that abnormal responses of airway smooth muscle contribute to the pathogenesis of airway obstruction in chronic obstructive pulmonary disease (COPD). For this purpose, lung tissue from 10 patients with and 10 patients without COPD was obtained during thoracotomies. Lung function was measured preoperatively. The in vitro responses of isolated bronchioles were measured using histamine, leukotriene (LT)C4, and methacholine as contracting agents, and the results of the in vitro measurements were compared between patients with and without COPD. Histamine efficacy (maximal isometric force, Tmax) in vitro of bronchioles from patients with COPD was significantly greater than the histamine Tmax of the bronchioles from patients without COPD (p < 0.01). This difference was probably not due to histamine tachyphylaxis or the production of relaxing prostaglandins by airways without COPD, as neither mechanism could be detected in separate experiments on airways without COPD. No differences were ...