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Figure 1 Endothelin-1 (ET-1) exerts vasoconstriction and proliferation via ET_A receptors on smooth muscle cells. Endothelial ET_B receptors mediate vasodilation via release of nitric oxide (NO) and prostacyclin. Endothelin_B receptors in the lung clear ET-1 from plasma. AI/II = angiotensin I/II; AT = angiotensin receptor; cAMP = cyclic adenosine monophosphate; cGMP = cyclic guanosine monophosphate; COX = cyclo-oxygenase; ECE = endothelin-converting enzyme; IL = interleukin; L-Arg = L-arginine; NOS = nitric oxide synthase; oxLDL = oxidized low density lipoprotein; PGI₂ = prostacyclin; SR = scavenger receptor; T = thrombin receptor; TGF = transforming growth factor; Thr = thrombin.