Inhibition of thrombin-induced contractile responses by protein kinase inhibitors in porcine pulmonary arteries

The clotting enzyme thrombin is known to cause receptor-mediated contractile effects in isolated blood vessels. In the present studies the influence of protein kinase inhibitors on the contractile response of porcine pulmonary arteries to thrombin (3 U/ml) was investigated. Endothelium-denuded rings (2-3 mm) from small arteries were placed in organ baths for isometric tension recording. The vessels were preincubated for 30 min with the inhibitors before inducing contractions. In the presence of the protein kinase C (PKC)-inhibitors staurosporine, BIM I (bisindolyl-maleimide I), chelerythrine and Ro 31-8220 (1 mu M each), the contractile responses to the PKC activator phorbol 12,13-dibutyrate (PDBu; 50 nM) were diminished by 70-100%. However, for inhibition of thrombin-induced contractions generally higher concentrations of the inhibitors were required. Only staurosporine at 1 mu M inhibited the thrombin effect by about 75%. The tyrosine kinase inhibitor erbstatin (30 mu M) did not significantly alter the thrombin effect, whereas genistein at 10 mu M caused a significant inhibition of contractile responses to both thrombin and PGF(2 alpha). At 100 mu M,genistein also inhibited the contractile effects of PdBu and KCL. These studies suggest that activation of both PKC and non-receptor tyrosine kinases seems to be involved in the signal transduction pathways of thrombin-induced contractile effects in isolated vessels.