Figure 2.

Effects of Up₄A on vascular smooth muscle functions. When EC are stimulated with, for example, ACh, ATP, uridine triphosphate (UTP), ET-1, mechanical stress or Ca²⁺ ionophore (A23187), Up₄A is generated. Released Up₄A acts in both ECs and vascular SMC. In ECs, Up₄A binds to P2Y1/2 or P1 receptor and activates endothelial nitric oxide synthase (eNOS); releasing NO and producing relaxation. In vascular SMCs, Up₄A leads to calcification, proliferation, migration, inflammation and contraction. Details are shown in text.