Endothelin-1-induced contractions of vascular and tracheal smooth muscle: effects of nicardipine and BRL 34915.

Endothelin-1 (ET-1) produced concentration-dependent contractions of rat aorta and rat trachea. These contractions were dependent on the presence of extracellular calcium but unaffected by nicardipine. Contractions of aorta could be attenuated with the potassium channel activator BRL 34915. BRL 34915 also elicited dose-related relaxations of rat aorta and trachea precontracted with ET-1. We conclude that although the increase in calcium permeability elicited by ET-1 may not involve dihydropyridine-sensitive calcium channels, its reversal by BRL 34915 suggests that smooth muscle contraction by ET-1 may involve a voltage-linked mechanism.