Abstract: AIM: To assess the influence of amlodipine on the expression of eNOS and iNOS on coronary vessels in myocardial I R model in hypercholesterolemia rats. METHODS: 64 healthy male Wistar rats were randomly divided into 4 groups:pure hypercholesterolemia group (Con), amlodipine group (AM), amlodipine +L-NAME group (AL), and amlodipine +sham group (Sham).Rats were fed with 3 %-4 % cholesterol and 15 %-20 % lard diet for 6 weeks.As dissecting thorax, the left coronary artery (LCA) was ligated for 30 minutes, and then followed a relaxation for 20 minutes or 2 hours.The expression of iNOS and eNOS was observed by immunohistochemical ABC method on endothelium of coronary vessels. RESULTS: Expression of eNOS and iNOS on endothelium of coronary vessels were marked positive, downregulated after ischemia 30 minutes, apparently increased after reperfusion 20 minutes, and reached the peak after reperfusion 2 hours in Con group.However, the effects were reversed partly by amlodipine.In AM group, the expression of NOS especially iNOS was downregulated significantly before ischemia (P<0.01), and then the expression of eNOS increased (P<0.01) while iNOS decreased (P>0.05) after ischemia 30 minutes.Both the expression of eNOS and iNOS was downregulated at the point of reperfusion 20minutes, followed an increase oparently but weaker than that in Con groups at 2 hours.In combined with L-NAME, the effect of amlodipine on eNOS and iNOS was partly prevented.CONCLUSION: Amlodipine is effective on hypercholesterolemic, myocardial postischemic and early reperfusion damage reduction, and most probably nitric oxide plays a determinant role in this effect.

Key words: ischemia reperfusion, nitric oxide, nitric oxide synthase, amlodipine hypercholesterolemia, endothelial cell, NG-nitro-L-Arginine-methyl-ester