CHARACTERIZATION OF CLONED HUMAN ENDOTHELIN RECEPTORS

Two subtypes of human endothelin receptors, ET(A) and ET(B), have been cloned and stably expressed in Chinese Hamster Ovary cells. These rec eptors have been characterized by [I-125]-endothelin-1 binding and pho sphatidyl inositol hydrolysis using the potent peptidyl ET(A) antagoni sts BQ-123 and BQ-153, as well as the potent ET(B) agonist, sarafotoxi n S6c. In binding studies, K(i) values for BQ- 123 and BQ-153 are 17 n M and 13 nM for ET(A) compared to 11, 100 nM and 7200 nM for ET(B). Co nversely, K(i) values for sarafotoxin S6c are 2800 nM for ET(A) and 0. 29 nM for ET(B). Endothelin-I stimulates phosphatidyl inositol hydroly sis in cells expressing either ET(A) or ET(B) with EC50 values of 0.2 - 0.3 nM, while sarafotoxin S6c stimulates phosphatidyl inositol hydro lysis only in ET(B) expressing cells with an EC50 value of 0.2 nM, con sistent with the binding data. Comparison of binding data for the clon ed and expressed human receptors with binding data for receptors obtai ned from human tissues indicates the cloned and expressed receptors ar e essentially indistinguishable from the naturally occurring receptors .