Effects of endothelin-1 on KCl-induced contractions of airway smooth muscles

The objective of the study was to investigate the effect of endothelin-1 (ET-1) on KCl-induced contractions. Tracheal strips were obtained from 12 male rabbits, perfused with Krebs solution and aerated continuously by bubbling with a mixture of 95% O2-5% CO2. Increasing concentrations of ET-1 (10-12-10-7 M) additionally to KCl caused more contractions than KCl-induced (P<0.05). A total of 10-7 M ET-1-induced 14.56% more contraction. Methylene blue (10-5 M) decreased all the contractions induced from simultaneous use of KCl and ET-1. Methylene blue caused about 18% relaxation of contraction induced from KCl (80 mM) and ET-1 (10-8 M). Consequently ET-1 increases the KCl-induced contractions of airway smooth muscles. This effect seem to mediate by a nitric oxide (NO)-guanylate cyclase-cGMP pathway, in which methylene blue is inactivator of guanylate cyclase. Copyright (C) 2000 Elsevier Science Ireland Ltd