Role of calcium ions on isolated ischaemic rabbit's heart after reperfusion

ABSTRACT

The role of Ca++ was evaluated on the heart rate during acute ischaemia and reperfusion of isolated heart of rabbits. Myocardial ischaemia was produced by induction of global ischaemia for 15 minutes followed by reperfusion for 360 minutes using physiological solution of normal, low, and high Ca++ concentrations. Perfusion of non ischaemic myocardium with physiological solution of different Ca++ ion containing high or low Ca++ concentration resulted in a non significant increase or decrease in heart rate respectively. Addition of verapamil [Ca++ channel blocker, CCB] to these physiological solutions resulted in a non significant change in heart rate when compared with the effect of physiological solution containing normal Ca++ concentration. Reperfusion of ischaemic myocardium after induction of global ischaemia by physiological solution containing normal Ca++ concentration resulted in significant tachycardia started immediately and continued for 4 hours. Also, reperfusion with physiological solution containing high Ca++ concentration resulted in significant tachycardia started immediately and continued for 2 hours, while reperfusion with physiological solution containing low Ca++ concentration resulted in a non significant change in heart rate. Addition of verapamil [CCB] to physiological solution containing either normal or low Ca++ concentration resulted in a significant bradycardiac effect, and this effect is delayed by using physiological solution containing high Ca++ concentration. From this work, it is clear that Ca++ may play a role as a cause of tachycardia during reperfusion of ischaemic myocardium. and the bradycardic effect of verapamil is not only due to its hypocalcemic effect. Also this effect of verapamil can be modified by using physio1ogica solutions of different Ca++ concentration, and indicates that Ca++ can share at least in part in the Pathophysiology of tachycardia during reperfusion ischaemic myocardium