Some bronchoconstricting and bronchodilating responses of human isolated bronchi: Evidence for the existence of α-adrenoceptors

Abstract

Isolated strips of human bronchi obtained during thoracic surgery exhibited pharmacological responses very similar to those of other species (e.g. guinea-pig). Analysis of the action of some sympathomimetic amines indicated that the human bronchi also possess a sparse population of α-adrenoceptors. Propranolol (>1 μg/ml) had a direct bronchoconstricting action, whereas another β-adrenoceptor blocking agent, alprenolol, produced bronchodilatation. Phentolamine (>4 μg/ml) also produced a bronchodilatation of its own. Theophylline and dibutyryl cyclic AMP produced dose-dependent relaxations. The strips were effectively contracted by acetylcholine, histamine, prostaglandin F2α (PGF2α), slow reacting substance (SRS) and bradykinin. Bradykinin, regardless of the dose, produced bronchoconstriction in some preparations and dilatation in others. 5-Hydroxytryptamine produced bronchodilatation but at very high concentrations a constriction was obtained.