Two kinds of receptors for Endothelin have been found, namely Endothelin-A (ET-A) receptor and Endothelin-B (ET-B) receptor. ET-A receptor is ET-1 specific and expressed in lung, aorta, atrium, liver, muscle, cerebral cortex, cerebellum, kidney, adrenal, duodenum, colon and placenta at the mRNA or cDNA level, while ET-B receptor lacks isopeptide specificity and is found in liver, lung, placenta, kidney, heart and brain.