Abstract
The involvement of endothelin ET A receptors in endothelin-1-induced contractions of the rabbit saphenous vein was studied. After desensitization of endothelin ET B receptors by pretreatment with sarafotoxin S6c, endothelin-1 and sarafotoxin S6b and a high concentration of endothelin-3 caused dose-dependent contractions. However, endothelin-1-induced contractions were much less sensitive to an endothelin ET A receptor antagonist, BQ-123 (cyclo (- d-Asp- l-Pro- d-Val- l-Leu- d-Trp-)), than sarafotoxin S6b-induced responses. The pA 2 values of BQ-123 for endothelin-1- and sarafotoxin S6b-induced contractions were 5.69 and 7.65, respectively. These results suggest pharmacological heterogeneity of endothelin ET A receptors in the rabbit saphenous vein.
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