Aim To investigate the effect of hyperhomocysteinemia on the expression of monocyte chemoattractant protein-1 in coronary endothelial artery cells in rats with hyperhomocysteinemia induced by excess methionine ingestion. Methods Twenty-four male Sprague-Dawley rats were randomly divided into 4 groups (n=6 for each group): Control group,High methionine group,High methionine+folate group and High cysteine group.They were fed with normal diet,normal diet enriched by 1.7% methionine,and normal diet plus 1.7% methionine and 0.006% folate,normal diet with 1.2% cysteine,respectively,for 6 weeks.The levels of total plasma homocysteine were measured by high performance liquid chromatography and the expression of monocyte chemoattractant protein-1 on coronary endothelial artery cells of rats was detected by immunohistochemistry. Results A high-methionine diet for 6 weeks induced hyperhomocysteinemia.The plasma homocysteine level was significantly higher in rats of High methionine group than in rats of Control group(P<0.01),and the expression of monocyte chemoattractant protein-1 in coronary endothelial artery cells was also stronger.During supplementation of folate,normalization of homocysteine levels was accompanied by a marked reduction of monocyte chemoattractant protein-1 expression in coronary endothelial artery cells in rats of High methionine+folate group(P<0.01),however,there were no significant differences in the plasma homocysteine and the expression of monocyte chemoattractant protein-1 in coronary endothelial artery cells between the Control group and the High cysteine group. Conclusions Hyperhomocysteinemia may play an important role in atherogenesis of coronary artery via stimulation of monocyte chemoattractant protein-1 expression in the coronary endothelial artery cells.