ROLE OF PLATELETS IN MYOCARDIAL ISCHEMIA-REPERFUSION INJURY IN DOGS

We investigated the involvement of circulating platelets in myocardial ischemia-reperfusion injury in canine autoperfused heart-lung prepara tions using filters to deplete platelets and/or leukocytes. The left a nterior descending (LAD) coronary artery was occluded for 40 min, foll owed by 40 min reperfusion, in 3 groups: a leukocyte-platelet-depleted (LPD) group, in which both leukocytes and platelets were depleted; a leukocyte-depleted (LD) group, in which leukocytes alone were depleted ; and a control group. There were no differences in hemodynamics or ar rhythmias among groups before or during coronary occlusion. After repe rfusion, the maximum rate of change in left ventricular pressure durin g systole and diastole was significantly higher in the LPD group than in the control and LD groups. The LPD group also showed gradual recove ry of regional myocardial function and a decrease in the frequency of premature ventricular contractions. The LD group showed a slight impro vement in cardiac function and arrhythmias compared with the control g roup. Although there was no significant difference in the pulmonary ar terial plasma level of thromboxane B-2 at any stage among groups, the control group showed an increase after reperfusion. These results sugg est that platelets are important in reperfusion injury and that the de pletion of both leukocytes and platelets effectively protects against reperfusion injury.