Fig. 1. (  A ) Diagram of an artery showing endothelial and vascular smooth muscle cells. (  B ) Mechanisms of endothelial-mediated dilations through nitric oxide (NO) and prostacyclin (PGI²). AC = adenylyl cyclase; cAMP = cyclic adenosine monophosphate; cGMP = cyclic guanosine monophosphate; COX = cyclooxygenase; eNOS = endothelial nitric oxide synthase; sGC = soluble guanylyl cyclase.