MYOCARDIAL PROTECTION BY ISCHEMIC PRECONDITIONING - THE INFLUENCE OF THE COMPOSITION OF MYOCARDIAL PHOSPHOLIPIDS

It was the aim of this study to investigate (1) whether preconditionin g modifies the fatty acid (FA) composition of myocardial phospholipids (PL), (2) whether a previous modification of membrane PL composition by the administration of coconut oil or fish oil influences the precon ditioning, and (3) to compare the protective effects of preconditionin g to those of dietary fish oil. To this end, three groups of rats were given during 10 weeks either a standard diet, or a standard diet +10% coconut oil, or a standard diet +10% fish oil. The preconditioning wa s performed in situ in the anesthetized open-chest rats by 2 cycles of 3 min left anterior descending coronary artery occlusion and 10 min r eperfusion. It was followed by a 40 min ischemia and a 60 min reperfus ion. ECG was recorded and used for the continuous count of the salves of extrasystoles, ventricular flutter and fibrillation. These rhythm d isturbances were subsequently added and evaluated as total arrhythmias . The FA of tissue PL were analyzed in a sample of the ischemic zone t he size of which was determined by means of malachite green. Coconut o il diet (rich in saturated FA) modified slightly the myocardial PL by increasing oleic acid acid and decreasing linoleic acid and resulted i n the highest incidence of arrhythmias. Fish oil diet had the opposite effect in modifying drastically the PLFA (replacement of the n-6 FA b y the n-3 FA) and minimizing significantly the arrhythmias in comparis on with the standard diet group. The antiarrhythmic effect of precondi tioning could be observed only after coconut oil had been administered and was not accompanied by a modification of PL composition. The redu ction of arrhythmias in this case was comparable to that observed unde r fish oil administration with and without preconditioning. The size o f the ischemic zone remained unchanged. We conclude that the protectio n by ischemic preconditioning is not mediated by the modification of t he composition of heart PL, and that the n-3 FA diet had such a protec tive effect that no additional protection could be supplied by ischemi c preconditioning.