Proteinase-activated receptors 1 and 2 and the regulation of porcine coronary artery contractility: a role for distinct tyrosine kinase pathways.

Background And Purpose: Because angiotensin-II-mediated porcine coronary artery (PCA) vasoconstriction is blocked by protein tyrosine kinase (PYK) inhibitors, we hypothesized that proteinase-activated receptors (PARs), known to regulate vascular tension, like angiotensin-II, would also cause PCA contractions via PYK-dependent signalling pathways.

Experimental Approach: Contractions of intact and endothelium-free isolated PCA rings, stimulated by PAR1 /PAR2 -activating peptides, angiotensin-II, PGF2α , EGF, PDGF and KCl, were monitored with/without multiple signalling pathway inhibitors, including AG-tyrphostins AG18 (non-specific PYKs), AG1478 (EGF-receptor kinase), AG1296 (PDGF receptor kinase), PP1 (Src kinase), U0126 and PD98059 (MEK/MAPKinase kinase), indomethacin/SC-560/NS-398 (COX-1/2) and L-NAME (NOS).

Key Results: AG18 inhibited the contractions induced by all the agonists except KCl, whereas U0126 attenuated contractions induced by PAR1 /PAR2 agonists, EGF and angiotensin-II, but not by PGF2α , the COX-produced metabolites of arachidonate and KCl.

Parallel contractile signal transduction pathways activated by receptors for thrombin and epidermal growth factor-urogastrone in guinea pig gastric smooth muscle: blockade by inhibitors of mitogen-activated protein kinase-kinase and phosphatidyl inositol 3'-kinase.

Using a guinea pig gastric longitudinal smooth muscle preparation, we have compared the contractile signaling pathways triggered by the thrombin receptor-activating peptide, TFLLR-NH2 (TF) and by epidermal growth factor-urogastrone (EGF). In addition to inhibitors of tyrosine kinase [tyrphostin 47/AG213, genistein and the src-selective inhibitor CP118,556/PP1], cyclooxygenase (indomethacin, INDO) and diacylglycerol lipase (U57, 908), we also used the signal pathway probe inhibitors of mitogen-activated protein-kinase-kinase (MEK:PD98059), phosphatidylinositol 3'-kinase [PI3K: Wortmannin (WM) and LY294002], protein kinase C [PKC: GF109203X (GF)], and of the EGF-receptor kinase (PD153035). We found that in addition to the inhibition of both TF and EGF-stimulated contractions by the inhibitors of tyrosine kinase, cyclooxygenase and diacylglycerol lipase, the actions of TF and EGF were also attenuated by PD98059, WM/LY294002 and GF.