Specific features of epithelium-dependent contractile reactions of smooth muscles in various subdivisions of the respiratory tract

Abstract

Characteristic features of the endothelium-dependent smooth muscle contractile reactions to various physiologically active substances modulating adrenergic, cholinergic, and histaminergic regulatory systems are studied in rabbit trachea and in secondary and tertiary bronchi. The mechanical tension of the segments was recorded under quasi-isometric conditions. The epithelium was shown to participate in adrenergic regulation of the smooth muscles of the lower subdivisions of the respiratory tract and in the cholinergic regulation of its upper subdivisions. The histaminergic reactions of the smooth muscles in the airways had large amplitude at all levels, but the relaxing contribution of their epithelium was not detected.