Myocardial protection by ischemic preconditioning: The influence of the composition of myocardial phospholipids

It was the aim of this study to investigate (1) whether preconditioning 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 preconditioning, and (3) to compare the protective effects of preconditioning 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 was performedin situ in the anesthetized open-chest rats by 2 cycles of 3 min left anterior descending coronary artery occlusion and 10 min reperfusion. It was followed by a 40 min ischemia and a 60 min reperfusion. ECG was recorded and used for the continuous count of the salves of extrasystoles, ventricular flutter and fibrillation. These rhythm disturbances were subsequently added and evaluated as total arrhythmias. The FA of tissue PL were analyzed in a sample of the ischemic zone the size of which was determined by means of malachite green.Coconut oil diet (rich in saturated FA) modified slightly the myocardial PL by increasing oleic acid acid and decreasing linoleic acid and resulted in the highest incidence of arrhythmias. Fish oil diet had the opposite effect in modifying drastically the PLFA (replacement of the n-6 FA by the n-3 FA) and minimizing significantly the arrhythmias in comparison with the standard diet group. The antiarrhythmic effect of preconditioning could be observed only after coconut oil had been administered and was not accompanied by a modification of PL composition. The reduction of arrhythmias in this case was comparable to that observed under fish oil administration with and without preconditioning. The size of the ischemic zone remained unchanged.We conclude that the protection by ischemic preconditioning is not mediated by the modification of the composition of heart PL, and that the n-3 FA diet had such a protective effect that no additional protection could be supplied by ischemic preconditioning.Abbreviations 120 lauric acid - 140 myristic acid - 160 palmitic acid - 161 n-7 t-trans-palmitoleic acid - 161n-7 c cis-palmitoleic acid - 180 stearic acid - 181n-9 oleic acid - 181n-7 vaccenic acid - 182n-6 linoleic acid - 183n-3- linolenic acid - 203n-6 dihomo -linolenic acid - 204n-6 arachidonic acid - 205n-3 eicosapentaenoic acid (EPA) - 224n-6 eicosatetraenoic acid - 225n-3 docosapentaenoic acid (DPA) - 226n-3 docosahexaenoic acid (DHA) - BHT butylated hydroxytoluene