Endothelium-dependent and -independent responses to protease-activated receptor-2 (PAR-2) activation in mouse isolated renal arteries.

Protease-activated receptors (PARs) are receptors which require proteolytic cleavage to be self-activated by newly exposed N-terminal 'tethered ligands', and hence serve as sensors for protelytic enzymes. While both the thrombin receptor (PAR-1) and PAR-2 (activated by tryptic enzymes) have been shown to mediate endothelium-dependent vasorelaxation, only PAR-1 has been shown to cause direct vascular smooth muscle contraction. In this study, we report that trypsin and the PAR-2 selective peptide ligand SLIGRL-NH2 not only caused endothelium-dependent relaxation of mouse renal arteries but also direct smooth muscle contraction if endothelial nitric oxide synthase was inhibited or if the endothelium was removed.