Abstract: Objective To explore the mechanisms responsible for different coronary artery lesions involved in nitric oxide (NO), endothelin -1 (ET-1), matrix metalloproteinases -9 (MMP-9) and the matrix metalloproteinase inhibitor -1 (TIMP -1). Methods The cases undergone coronary anography in our hospital were collected and divided into three groups: group A,30 patients with the coronary artery ectasia(7 cases of simple coronary artery ectasia; 18 cases of the coronary artery ectasia coexisting a small amount of plaque)；group B,38 patients with coronary atherosclerosis; group C,32 patients with with normal angiograph (14 cases of coronary artery completely normal; 18 cases with a small amount of coronary plaque only). Plasma NO, ET-1, MMP-9 and TIMP-1 level were measured by ELISA method. Results There are significant differences among three groups on NO level, MMP-9 levels, NO/ET-1 and MMP-9/TIMP-1 (P< 0.05). Further sub-group analysis, NO advanced to peak value in isolated coronary ectasia, while MMP-9 rose to highest value in the coronary artery ectasia coexisting a small amount of plaque. Conclusions The coronary ectasia may be the normal compensatory function to resist the coronary artery atherosclerosis ,while coronary atherosclerosis is the lower of compensatory function.

Key words: NO, ET-1, MMP-9, TIMP-1, coronary artery ectasia, coronary atherosclerosis