Subtype selectivity of a novel endothelin antagonist, FR139317, for the two endothelin receptors in transfected Chinese hamster ovary cells

We investigated the receptor-binding properties and the antagonist activities of FR139317, a novel endothelin (ET) antagonist, in transfected Chinese hamster ovary cells permanently expressing the two ET receptor subtypes (ETA and ETB). In displacement analysis using membrane preparations derived from the receptor-expressing cells, FR139317 showed a high affinity for ETA (Ki = 1 nM) and a lower affinity for ETB (Ki = 7.3 microM). FR139317 inhibited ETA-mediated phosphatidylinositol hydrolysis and arachidonic acid release and produced a parallel shift in the dose-response curve for ET-1, with respective pA2 values of 8.2 and 7.7. In contrast, FR139317 had no inhibitory effects on these ET-1-induced responses in ETB-expressing cells. FR139317 itself showed no stimulatory effects on phosphatidylinositol hydrolysis and arachidonic acid release in ETA- and ETB-expressing cells. Thus, FR139317 is a potent, competitive, and highly selective antagonist for ETA. This compound should be a powerful tool for investigation of the physiological properties of ETA and exploration of its role in diseases.