Individual effects of dietary EPA and DHA on the functioning of the isolated working rat heart

The aim of this study was to evaluate the effects of dietary pure eicosapen taenoic acid (EPA) and docosahexaenoic acid (DHA) on the physiology of the heart in normoxic conditions and during postischemic reperfusion. These eff ects were compared with those of dietary n-6 polyunsaturated fatty acids (P UFA). Rats were fed a diet containing either sunflower seed oil (75 g.kg(-1 ), SSO group), or a mixture of EPA (20:5 n-3) ethyl ester and SSO (10:90, E PA group), or a mixture of DHA (22:6 n-3) ethyl ester and SSO (10:90, DHA g roup), or a mixture of EPA + DHA ethyl esters and SSO (4.2:5.8:90, (e)+D gr oup) for 6 weeks. The hearts were then perfused according to the working mo de. The perfusion was maintained either in normoxic conditions or stopped f or 17 min (global zero-flow ischemia) and restored for 33 min (reperfusion) . The aortic and coronary flows, aortic developed pressure, and electrocard iogram were continuously monitored. When rats were fed a diet containing ei ther EPA and (or) DHA, the n-6/n-3 PUFA ratio of cardiac phospholipids decr eased. The proportion of arachidonic acid was reduced more with DHA than di etary EPA. In the EPA group, the percentage of DHA was lower than in the DH A group, but the percentage of EPA and docosapentaenoic acid (22:5 n-3) was higher. These changes in membrane fatty acid composition altered the cardi ac function. In normoxic conditions, the coronary flow was higher in the SS O group than in the DHA and EPA groups. The heart rate was lower in the DHA and (e)+D groups than in the EPA and SSO groups. The aortic flow, cardiac output, and aortic developed pressure were not affected. During postischemi c reperfusion, the recovery of aortic flow, coronary flow, and aortic devel oped pressure was similar in the four groups. A slightly improved recovery of cardiac function was noticed in the EPA group, but the difference was no t significant. Feeding rats 5% fish oil + 5% SSO instead of 10% SSO for 8 w eeks increased the incorporation of EPA in cardiac phospholipids and favore d the recovery (+120%) of aortic flow during postischemic reperfusion. In c onclusion, the beneficial effect of dietary fish oil on the recovery of car diac pump activity during reperfusion was not observed with DHA or EPA alon e. It appears to be positively related to the accumulation of EPA in membra ne phospholipids. The dietary conditions favouring EPA accumulation remain to be determined.