Interaction between adenosine diphosphate receptors and protein-kinase C isoforms in platelet adhesion under flow condition

Abstract

Adenosine diphosphate (ADP) receptors and protein-kinase C (PKC) isoforms play different role in platelet activity. In the present study, whole blood platelet adhesion at 200 - 1800 s-1 shear rates was investigated by Impact-R system, measuring percent of surface coverage (SC) by platelets. Gradual heightened shear rate par-alleled increase of platelet adhesion. At relatively low shear (200 and 1000 s-1) blockade of neither P2Y1 receptor nor P2Y12 receptor (by A2P5P and 2MeSAMP, respectively) affected SC. At high shear rate (1800 s-1) reduction of SC was observed by 2MeSAMP. Treatment of blood with PKCδ inhibitor (rottlerin) but not PKCα,β inhibitor (Gö6976) diminished platelet adhe-sion. Among all the agents, only combination of 2MeSAMP and rottlerin used at subthreshold concentrations was able to inhibit platelet adhesion under high shear condition. We suggest that platelet agonist-induced P2Y12 and PKCδ signaling essentially stimulates platelet adhesion under flow condition, the important initiating step of thrombin formation.