Abstract: Objective To observe the effects of 11, 12-epoxyeicosatrienoic acid (11, 12 -EET) on heme oxygenase-1(HO-1) in myocardial ischemic/reperfusion(I/R) injury in rats. Methods Myocardial ischemic/reperfusion model was produced by legating the left anterior descending coronary artery for 60 min followed by 30 min reperfusion. The rats were divided into 3 groups: 1) ischemia/ reperfusion(I/R) group; 2) EET group, 6.24×10^-8 mol/ L 11, 12-EET was injected intravenously 20 min before I/R; 3) L-NAME group, L-NAME was injected intravenously 10 min before EET plus I/R .The heart function was evaluated by observing the change of +dp/dtmax and -dp/dtmax. The level of HO-1 was detected by Western blot method. The activities of nitric oxide synthase of myocardium were examined by colorimetric method. Results At 30 min reperfusion, +dp/dtmax and -dp/dtmax increased significantly in EET group compared with I/R group(P<0.01). HO-1 level was higher in EET group than I/R group(P<0.05). HO-1 level was lower in L-NAME group than EET group(P<0.05). The activities of cNOS in EET group were higher than those in I/R(P<0.01). The activities of iNOS in EET group were lower than those in I/R(P<0.01). Conclusion 11, 12-EET protected rat heart against I/R injury. 11,12-EET increased the expression level of HO-1 and the activities of cNOS and decreased the activities of iNOS .As the expression of HO-1 induced by 11,12-EET could be blocked by L-NAME, It was indicated that elevated HO-1 was involved in NO-meadiated signal pathway.

Key words: 12-epoxyeicosatrienoic acid, cardiac muscle, ischemic/reperfusion, heme oxygenase-1, nitric oxide synthase