Abstract: SIPI-549 is a new cOmpound. In Langendorff's isolated rabbit heart, SIPI-549 significantly increased coronary blood flow (p<0.01), but did not change themyocardium contractibility and heart rate. A study of the uptake of ~(86)Rb by the mouse heart showed a significant increase of nutritional blood flow in the SIPI-549 treated group (p<0.05). On intact dogs, SIPI-549 also showed a significant increase of coronary blood flow (p<.05) and decrease of coronary resistance (p<0.01), but no change of cardiac output and blood presure was observed.In the model of myocardial infarction by high level double-ligation of the anterior descending branch of the left coronary in rabbits, iv SIPI-549 (4.1 mg/kg) significantly reduced the ΣST, NST and NO The size of infarct myocardium was significantly reduced (p<0.05) 24 h after ligation of the coronary artery Similar results were found in the propranolol (1 mg/kg) group. However, no obvious difference between the two groups was observed.