DETECTION OF FUNCTIONAL RECEPTORS FOR THE PROTEINASE-ACTIVATED-RECEPTOR-2-ACTIVATING POLYPEPTIDE, SLIGRL-NH2, IN RAT VASCULAR AND GASTRIC SMOOTH-MUSCLE

We have studied the actions of the proteinase-activated-receptor-2 (PAR(2))-activating polypeptide, SLIGRL-NH2 (SLI-NH2), in rat aorta and in gastric longitudinal muscle preparations. In the phenylephrine-precontracted aorta preparation, SLI-NH2 caused an endothelium-dependent relaxation that mimicked the action of low concentrations (0.5 U/mL) of trypsin and that was blocked by the nitric oxide synthase inhibitor N-omega-nitro-L-arginine methyl ester. In endothelium-free aorta ring preparations, SLI-NH2 caused neither a relaxation nor a contraction. In the gastric longitudinal muscle preparation, SLI-NH2 caused a transient contraction that mimicked the action of trypsin (0.5 U/mL) and that was sensitive to inhibitors of cyclooxygenase (indomethacin) and tyrosine kinase (genistein). Further, using a reverse-transcriptase - polymerase chain reaction (RT-PCR) approach we detected, in both assay tissues, mRNA for the rat PAR(2) receptor, and we ascertained, using a cloned receptor cDNA obtained from a rat intestinal cDNA library, that the putative N-terminal activating peptide sequence of the rat PAR(2) receptor (SLIGRL) is identical with the one previously cloned from murine tissue. We concluded that, like the thrombin receptor, the PAR(2) receptor may play a pathophysiologic role in the regulation of vascular and gastric smooth muscle contractility.