Pharmacological evidence for distinct endothelin receptors in guinea‐pig bronchus and aorta

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Abstract
The ETA receptor antagonist, BQ-123 (1 μm) potently antagonized endothelin-1 (ET-1) concentration-response curves in guinea-pig aorta (pKB = 7.1). However, 10 μm BQ-123 was without effect on ET-1-induced contractions in guinea-pig bronchus. The ETB-selective agonist, sarafotoxin S6c did not contract the aorta but was a potent and effective contractile agonist in the bronchus. BQ-123 (10 μm) 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 ETA and non-ETA, perhaps ETB, subtypes, respectively.