Vasoconstrictor effect of endothelin-1 in human skin: role of ETA and ETB receptors.

The aim of this project was to investigate the role of ETA and ETB receptors in the mediation of endothelin (ET)-1-induced vasoconstriction in human skin. This information should provide important insights into the design of pharmacological intervention against skin vasospasm induced by ET-1 in peripheral vascular disease or surgical trauma. Vasoconstriction in response to intra-arterial drug infusion in isolated perfused human skin flaps (8 x 18 cm) derived from dermolipectomy specimens was assessed by studying changes in skin perfusion and perfusion pressure under constant flow rate in each drug treatment (n = 4). It was observed that ET-1 (10(-10) to 10(-8) M) and norepinephrine (NE, 10(-8) to 10(-5) M) caused skin vasoconstriction in a concentration-dependent manner, with the vasoconstrictor potency of ET-1 approximately 200-fold higher than NE. The ETA-receptor antagonist BQ-123 but not the ETB-receptor antagonist BQ-788 blocked the vasoconstrictor effect of ET-1. This observation was confirmed by studying skin perfusion using the dermofluorometry technique. In addition, ETB-receptor agonists BQ-3020 and sarafotoxin S6c (10(-9) to 10(-6) M) did not evoke skin vasoconstriction. BQ-3020 also did not elicit skin vasoconstriction even in the presence of 10(-5) M of Nomega-nitro-L-arginine methyl ester and indomethacin. Furthermore, results from saturable and competitive ET-1 radioligand membrane receptor binding assays revealed that high-affinity and capacity binding sites are predominantly the ETA receptor subtype in endothelium-denuded skin arteries and veins of 0.5-1.5 mm diameter, with an ETA-to-ETB receptor ratio of 83:17 in arteries (n = 5) and 78:22 in veins (n = 7). Results from the present functional and radioligand receptor binding studies clearly indicate that ET-1 is a very potent vasoconstrictor in human skin and its vasoconstrictor effect is primarily mediated by ETA receptors, with no significant participation from ETB receptors.