Preparation of bovine tracheal smooth muscle for in vitro pharmacological studies

In this study a new method is described for standardization of both length and weight of bovine tracheal smooth muscle strips to be used for measuring airway responsiveness in vitro. Tracheal smooth muscle was cut into strips 2.5-mm thick and 10-mm long with an average wet weight of 25.9 +/- 0.6 mg (n = 5). By use of preloads varying from 0.5 to 10 g, it was found that 5 g caused the highest contraction and relaxation of the tissues in response to pharmacological agents. Moreover, at a preload of 5 g the variations among the maximal responses induced by histamine, methacholine, KCl, and salbutamol were very small (standard errors being 6.8%, 5.0%, 2.5%, and 1.6% of the corresponding average maximal response) as well as were the variations in the pD2 values.