PHARMACOLOGICAL EVIDENCE FOR DISTINCT ENDOTHELIN RECEPTORS IN GUINEA-PIG BRONCHUS AND AORTA

The ET(A) receptor antagonist, BQ-123 (1-mu-M) potently antagonized endothelin-1 (ET-1) concentration-response curves in guinea-pig aorta (pK(B) = 7.1). However, 10-mu-M BQ-123 was without effect on ET-1-induced contractions in guinea-pig bronchus. The ET(B)-selective agonist, sarafotoxin S6c did not contract the aorta but was a potent and effective contractile agonist in the bronchus. BQ-123 (10-mu-M) was without effect on sarafotoxin S6c-induced contractions in the bronchus. These data provide evidence for distinct endothelin receptors in guinea-pig aorta and bronchus, which appear to be predominantly of the ET(A) and non-ET(A), perhaps ET(B), subtypes, respectively.