Effect of dietary polyunsaturated fatty acids on contractile function of hearts isolated from sedentary and trained rats

Moderate physical training induced a decrease in arterial blood pressure in fish oil-fed rats as compared to sunflower seed oil-fed rats [14]. The pur pose of this study was to determine if these changes were due to modificati ons of the left ventricular function of the heart. Forty rats were fed a se mi-purified diet containing either 10% sunflower seed oil or 10% fish oil ( EPAX 3000TG, Pronova). Each dietary group was assigned to two sub-groups, o ne being constituted by sedentary animals and the other by trained animals. Training was achieved by daily running for 60 minutes at moderate intensit y for three weeks. At the end of the training period, the animals were sacr ificed and their hearts were immediately perfused according to the working mode. The phospholipid fatty acid composition and parameters of the left ve ntricular function were determined. Feeding fish oil markedly reduced the p roportion of n-6 polyunsaturated fatty acids (PUFA, 18:2 n-6, 20:4 n-6, 22: 4 n-6 and 22:5 n-6) in cardiac phospholipids. The n-6 PUFA were replaced by n-3 PUFA (mainly docosahexaenoic acid). In sedentary animals, the fluid dy namic (aortic and coronary flow, cardiac output) was not modified by the di et. The heart rate was reduced (-10%) in n-3 PUFA-rich hearts. Physical tra ining did not markedly alter the polyunsaturated fatty acid profile of card iac phospholipids. Conversely, it reduced the heart rate, aortic flow and c ardiac output (-11, -21 and -14%, respectively) at a similar extent in the two dietary groups. In a second set of experiments, the training period was repeated in animals fed a commercially available diet (A103, UAR) which si multaneously provided n-6 and n-3 fatty acids. In these dietary conditions, neither the aortic flow nor the heart rate was decreased by physical exerc ise. These results suggest that both n-6 and n-3 PUFA in the diet are neces sary to ensure a good cardiac adaptation to moderate physical training. Fur thermore, the fish oil-induced decrease in arterial blood pressure in train ed animals was not related to changes in cardiac contractility, but to a de crease in vascular resistances. Moderate physical training + dietary n-3 PU FA might be used to prevent hypertension and cardiovascular diseases.