Ventricular histamine concentrations and arrhythmias during acute myocardial ischaemia in rats

The relation between ventricular histamine concentrations and the occurrence of early ventricular arrhythmias during acute myocardial ischaemia was investigated in pentobarbitone-anaesthetized rats. There was significant decrease in the left, but not the right, ventricular histamine level at 5 min following acute left coronary artery ligation. Pretreatment with rhodanine caused remarkable reduction in ventricular histamine concentrations as well as significantly lower incidence and slower onset of ventricular tachycardia and fibrillation resulting from acute myocardial ischaemia. On the contrary, aminoguanidine pretreatment did not significantly alter ventricular histamine levels nor did it influence the occurrence of early ventricular arrhythmias induced by coronary artery ligation. The responses of blood pressure and heart rate to acute coronary artery ligation were not noticeably affected by rhodanine or aminoguanidine pretreatment. These findings support the hypothesis that histamine release from cardiac tissues may contribute to the genesis of early ventricular arrhythmias, but not to the changes in blood pressure and heart rate, during acute myocardial ischaemia.