Effects of verapamil on histamine-and carbachol-induced contraction of pulmonary tissues in vitro.

It has been hypothesized that calcium antagonists may be useful in the management of airway hyperreactivity. In these studies, we evaluated the effects of verapamil on guinea pig tracheal spirals and parenchymal lung strips in vitro. Preincubation of both tissues with verapamil caused concentration-dependent inhibition of contraction with significant effects noted at a 10 micromolar concentration. At this concentration of verapamil, approximately fivefold greater concentrations of either histamine or carbachol were required to produce contraction of tracheal spirals; and 21-fold greater concentrations of histamine and 630-fold greater concentrations of carbachol were required to contract parenchymal strips. We also assessed the ability of verapamil to reverse contraction. Significant reversal of both histamine- and carbachol induced contraction was observed with concentrations of 3 micromolar verapamil and contraction was nearly abolished with a 100 micromolar concentration. These data demonstrate that verapamil can both inhibit airway contraction and reverse contraction once it is present and further suggest that verapamil or other calcium antagonists may prove useful in the management of airway hyperreactivity.