Abnormalities in airway smooth muscle in fatal asthma. A comparison between trachea and bronchus.

Tracheal smooth muscle from seven cases of fatal asthma demonstrated an increased contractile response to histamine, acetylcholine, and electrical stimulation of intrinsic cholinergic nerves; impaired relaxation to isoproterenol, and possibly theophylline, was also evident (1). Fourth generation bronchial spirals from the same patients were also studied, and these results were compared with those of the trachea and normal bronchi (n = 5). In contrast to trachea, contractile responses in asthmatic bronchi to acetylcholine, histamine, and cholinergic nerve stimulation were similar to those in control bronchi. The potency of isoprenaline (IC50) was reduced 9.4-fold (p less than 0.003), similar to trachea (4.5-fold), whereas theophylline responses were normal. The discrepant results obtained may reflect differences in the disease process, including rates of postmortem change, at the two anatomic sites.