Signal transduction pathways involved in the mechanical responses to protease-activated receptors in rat colon.

Recording simultaneously in vitro the changes of endoluminal pressure (index of circular muscle activity) and isometric tension (index of longitudinal muscle activity), we examined the mechanisms responsible for the apamin-sensitive relaxant and contractile responses induced by protease-activated receptor (PAR)-1 and PAR-2 activating peptides, SFLLRN-NH2 and SLIGRL-NH2, respectively, in rat colon. In the circular muscle, the inhibitory effects of SFLLRN-NH2 and SLIGRL-NH2 were significantly reduced by ryanodine, an inhibitor of Ca2+ release from the sarcoplasmic reticulum, but unaffected by 1-[6-[[17beta-methoxyestra-1,3,5(10)-trien-17-yl]amino]hexyl]-1H-pyrrole-2,5-dione (U73122), a phosph…