| Abstract: | The effect of high- and low-density lipoproteins separated from human serum on the postischemic reperfusion arrhythmias was investigated. The hearts were perfused by working heart mode with Krebs Henseleit bicarbonate buffer containing arachidonic acid (1 μg/ml) for 5 minutes. Whole heart ischemia was induced by the use of a one-way ball valve, and hearts were perfused for 15 minutes followed by 20 minutes of reperfusion. Physiologic concentrations of high- and low-density lipoproteins were constantly infused through the atrial route during ischemic perfusion. Coronary effluent was collected via pulmonary artery cannulation for subsequent radioimmunoassay of thromboxane B2 and 6-keto-prostaglandin F1α, the major stable metabolites of thromboxane A2 and prostacyclin, respectively. The incidence of ventricular arrhythmias during reperfusion was 6/6 (100%), 1/6 (17%), and 6/6 (100%) in control, high-density lipoprotein and low-density lipoprotein infusion groups, respectively. There was no significant difference in coronary flow among the three groups throughout the perfusion. Both thromboxane B2 and 6-keto-prostaglandin F1α increased significantly during ischemia compared with preischemic values in all groups of hearts. However, the ratio of these two parameters varied in control and low-density lipoprotein infusion groups during ischemia, while there was no significant change in the high-density lipoprotein infusion group. These results provide the possibility that arachidonate metabolites may be involved in the regulation of ischemia-reperfusion arrhythmias and that high-density lipoprotein that was infused during ischemia markedly inhibits the incidence of ischemia-reperfusion-induced ventricular arrhythmias, due in part at least, to stabilizing the arachidonate metabolites during ischemic perfusion. |
