Effect of reduced calcium on lysophosphatidylcholine-induced cardiac arrhythmias.

Lysophosphatidylcholine (LPC) had recently been shown to accumulate in the ischemic heart and was demonstrated to be arrhythmogenic in perfused hearts. The present study was designed to examine the effects of calcium and verapamil on LPC-induced arrhythmias. Rat hearts were perfused through the aorta with oxygenated Krebs-Henseleit buffer at 37 degrees C. The occurrence of ventricular fibrillation was dependent on the LPC concentration and perfusion time. In subsequent experiments, each heart was perfused with a buffer containing 20 microM LPC for 3 min and was followed with a 10 min washout period. Ventricular fibrillation occurred in all 8 control experiments. When the Ca2+ concentration was reduced to half, only 3 out of 8 hearts fibrillated. In the presence of 0.2 mg/1 of verapamil, 7 out of 9 hearts fibrillated, and the time to fibrillation was not increased significantly by verapamil. These results suggest that calcium may be important in LPC-induced arrhythmias, and this effect is not significantly attenuated by the Ca2+ antagonist, verapamil.