Relaxation of human temporal artery by endothelin ETB receptors

Endothelin receptors have been characterized in human temporal artery by molecular biological methods and in vitro pharmacology. Reverse transcriptase-polymerase chain reaction was used to detect mRNA encoding ETA and ETB receptors in normal and endothelium-denuded arteries. Vasomotor response experiments with a specific ETA antagonist (FR 139317) suggested the presence of ETA subtypes. Marked ETB-mediated relaxation was obtained with ET-3 when ETA activity was blocked in precontracted arteries. Relaxation was significantly reduced by bosentan, indomethacin, and a nitric oxide synthase inhibitor. It may be speculated that the relaxant activity is mediated through ETB1 receptors.