ABSTRACT
Recent studies revealed an additive cardiodepressive effect of polymorphonuclear granulocytes (PMN) and thrombocytes in hearts exposed to a no-flow ischemia. To find out whether or not this is also true for isolated guinea pig hearts exposed to a low-flow ischemia, the current study was performed. PMN or thrombocytes, together or separately, were applied as a 1-min bolus (1,000/microl or 20,000/microl, respectively) during ischemia or in reperfusion in the presence of thrombin (0.3 U/ml perfusate). Recovery of external heart work and intracoronary cell retention were quantified in percent. Sole application of PMN or platelets during ischemia and reperfusion significantly compromised myocardial function, whereas coapplication of PMN and platelets did not exhibit any further cardiodepressive effect. Coapplication of cells almost prevented intracoronary platelet retention during ischemia and in reperfusion, as opposed to sole platelet application. Known blockers of endogenously released anti-platelet substances like nitric oxide, PGI(2) or adenosine did not mediate a further aggravation of myocardial dysfunction. The platelet-activating factor (PAF) antagonist WEB 2170 BS, however, significantly improved recovery of external heart work during ischemia and in reperfusion. This indicates that an additive cardiodepressive effect of PMN and platelets in working guinea pig hearts exposed to a low-flow ischemia, cannot be demonstrated, whereas PAF antagonists seem to be cardioprotective, under these conditions. Even addition of fibrinogen to the perfusate, did not show an additive cardiodepressive effect of coapplication of PMN and platelets.
Subject(s)
Blood Platelets/metabolism , Myocardial Reperfusion Injury/metabolism , Myocardial Reperfusion Injury/pathology , Myocardium/metabolism , Neutrophils/metabolism , Animals , Cell Adhesion/drug effects , Cell Adhesion/immunology , Fibrinogen/pharmacology , Guinea Pigs , In Vitro Techniques , Myocardial Contraction , Myocardium/pathology , Platelet Adhesiveness , Reactive Oxygen Species/metabolismABSTRACT
In recent studies, we could demonstrate a myocardial dysfunction induced by homologous platelets in ischemic and reperfused guinea pig hearts. Aim of the current study was to find out whether or not this is a phenomenon specific for platelets isolated from guinea pigs and to further examine the mechanisms of a possible cardiodepressive effect of human platelets. Isolated guinea pig hearts were exposed to a 30 min low-flow ischemia (1 ml/min) and reperfused. Human thrombocytes were administered as bolus (20.000 thrombocytes/microl perfusion buffer) in the 15(th) min of ischemia or in the 1(st) or 5(th) min of reperfusion in the presence of thrombin. Recovery of external heart work (REHW) and intracoronary platelet retention (RET) were quantified in percent. In additional experiments, the GPIIb/IIIa-blocker tirofiban (10 microg/ml perfusion buffer) or the radical scavenger superoxide dismutase (SOD-10 U/ml perfusion buffer) were added. Platelet application in the absence of tirofiban, either during ischemia (REHW 75.4 +/- 4%, RET 22.2 +/- 2%) or the 1st min (REHW 71.6 +/- 1%, RET 31.2 +/- 2%) or the 5th min of reperfusion (REHW 63.2 +/- 4%, RET 40.5 +/- 1%) led to a significant reduction of REHW and a significant increase of RET. The coapplication of tirofiban, on the other hand, prevented RET at all three times of platelet application (1.1 +/- 1.7%, 0% or 2.1 +/- 1.2%, respectively). An improvement of REHW, however, could only be noticed during ischemia (89 +/- 2%), whereas coapplication of tirofiban in early (72.9 +/- 3%) or in late reperfusion (74.6 +/- 2%) did not lead to a significant increase of REHW. Coapplication of SOD, on the other hand, significantly improved REHW in early (88.1 +/- 1) or late (95.9 +/- 1) reperfusion but not during ischemia (83.5 +/- 2). Corresponding to REHW, RET was changed significantly by coapplication of SOD during early (1 +/- 2%) or late (0%) reperfusion but not during ischemia (21.1 +/- 4%). We conclude that human thrombocytes are able to induce a myocardial dysfunction in ischemic and reperfused guinea pig hearts mediated by reactive oxygen species and independent of intracoronary platelet adhesion.
