Protease-activated receptor-2 involvement in hypotension in normal and endotoxemic rats in vivo.

Background—The protease-activated receptor-2 (PAR-2) is expressed by vascular endothelial cells and upregulated by lipopolysaccharide (LPS) in vitro. PAR-2 is activated by a tethered ligand created after proteolytic cleavage by trypsin or experimentally by a synthetic agonist peptide (PAR-2AP) corresponding to the new amino terminus of the tethered ligand. Methods and Results—Intravenous administration of PAR-2AP (0.1, 0.3, and 1 mg/kg) to rats caused a dose-dependent hypotension. A scrambled peptide was without effect. A specific trypsin inhibitor, biotin–SGKR-chloromethylketone, inhibited trypsin-induced hypotension but not that stimulated by PAR-2AP. In animals treated with LPS 20 hours earlier, we found an increased sensitivity to trypsin and PAR-2AP in the hypotensive response. In particular, PAR-2AP caused hypotension at a low concentration of 30 ng/kg. Moreover, PAR-2 was immunolocalized to endothelial and smooth muscle cells in aorta and jugular vein in LPS-treated rats, and increased levels of PA...