Comparison of human bronchiolar smooth muscle responsiveness in vitro with histological signs of inflammation.

A study was carried out to test the hypothesis that chronic inflammation is associated with increased sensitivity or contractility of human airway smooth muscle. Bronchiolar strips from 30 patients, 12 of whom had chronic bronchitis, were examined in the organ bath for their responses to histamine, methacholine, and leukotriene (LT) C4. The same airways were also studied histologically and small airway disease was quantified by subjective grading of the degree of inflammatory cell infiltration, smooth muscle hypertrophy, fibrosis, and goblet cell hyperplasia. The degree of small airway disease varied widely among patients both with and without chronic bronchitis. Multiple regression analysis failed to show increased sensitivity (-log EC50) to histamine, methacholine, or LTC4 in relation to small airway disease. In contrast, the only significant correlations found were between a decreased -log EC50 to histamine and methacholine and an increased small airway disease score. Contractile responses (Tmax) to histamine and methacholine in peripheral airways tended to be higher in patients with chronic bronchitis than in those without. Tmax was not related to small airway disease scores. These results suggest that chronic airway inflammation does not cause in vitro hyperresponsiveness of human small airway smooth muscle.