ENDOTHELIN RECEPTOR SUBTYPES ARE COUPLED TO ADENYLATE-CYCLASE VIA DIFFERENT GUANYL NUCLEOTIDE-BINDING PROTEINS IN VASCULATURE

We have studied whether endothelin (ET) isopeptides have any effects on adenylate cyclase activity via different guanyl nucleotide-binding proteins (G-proteins) in cultured rat vascular smooth muscle cells (VSMC) and bovine endothelial cells (EC). Northern blot analysis clearly demonstrated gene expression of ETA receptors in VSMC and ET(B) receptors in EC. ET-1 dose-dependently (10(-9)-10(-6) M) stimulated cAMP formation in VSMC, whose effect was inhibited completely by ET(A) receptor antagonist (BQ-123) but not by indomethacin or quinacrine. The ET-1-induced cAMP formation was additive with isoproterenol but not with cholera toxin. In contrast, ET-3 and ET(B) receptor agonist (BQ-3020) dose-dependently (10(-9)-10(-6) M) inhibited forskolin-stimulated cAMP formation in EC, whose effect was completely abolished by pertussis toxin. Cholera toxin ADP ribosylated 45- and 52-kilodalton proteins in VSMC, whereas pertussis toxin ADP ribosylated the 41-kilodalton protein in EC. These data suggest that, in addition to phospholipase C via Gq, ET(A) and ET(B) receptor subtypes are functionally coupled to adenylate cyclase, possibly via Gs in VSMC and Gi in EC, respectively.