Endothelin ETA and ETB receptors mediate vascular smooth muscle contraction

Abstract

1 We have investigated the receptors mediating endothelin-induced contraction of rabbit isolated jugular vein (RJV) and rat isolated thoracic aorta (RTA). 2 Endothelin-1 (ET-1) and endothelin-3 (ET-3) contracted RJV preparations with similar potency (EC₅₀ values ∼ 1 nm), whereas, ET-1 (EC₅₀:4.5 nm) was ∼ 80 fold more potent than ET-3 in contracting RTA. In addition, the ET_B receptor-selective agonist [Ala^1,3,11,15]ET-l contracted RJV (EC₅₀:2.1 nm) but not RTA. 3 The ET_A receptor antagonist, BQ123, competitively antagonized (pA₂ 6.93) the contraction of RTA produced by ET-1, but had no effect (at 10 μm) on the contractile effects of either ET-1, ET-3 or [Ala^1,3,11,15]ET-1 in RJV. 4 These data suggest that both ET_A and ET_B receptors can mediate vascular smooth muscle contraction.