Abstract: Objective: To observe the changes of endothelin receptor in the heart of spontaneously hypertensive rats （SHRs）.Methods:Four months old rats were divided into two groups: SHRs （n=8） and WKY rats （n=8）. ¹²⁵I-ET-1 binding sites, affinity, and Hill coefficient in the cardiac membranes from left ventricle were examined by radio ligand binding study.Results:¹²⁵I-ET-1 binding site density in left ventricular membranes from SHRs was reduced （P＜0.05） as compared with that of WKY rats. There were no marked changes for KD and Hill coefficient between these two groups.Conclusion:These results suggest there are specific, high affinity, and a single population of endothlin-1 binding sites in left ventricular membranes from SHRs and WKY rats. In particular,¹²⁵I-ET-1 binding site density in left ventricle of SHRs is significantly lower than that of WKY rats.