RELAXATION BY DEXAMETHASONE OF ISOLATED GUINEA-PIG AIRWAYS PRECONTRACTED WITH ENDOTHELIN-1

Dexamethasone (1-100 muM) produced concentration-dependent relaxations of isolated guinea-pig tracheal and bronchial strips precontracted with endothelin-1 (100 nM), which were not affected by the removal of the epithelium. Dexamethasone neither induced relaxation of tissues precontracted with carbachol (0.1 muM) or KCl (25 mM) nor inhibition of endothelin-1 (1-100 nM)-induced peak contractions after 10-min preincubation of the tissues with dexamethasone. These findings indicate that acute corticosteroid treatment can reverse the bronchoconstrictor action of endothelin-1.