Aim. The study was designed to assess the efficiency of exogenous nitric oxide supply to the extracorporeal circulation line for myocardial protection against ischemic-reperfusion injury in acute myocardial infarction simulation during cardiopulmonary bypass (CPB) in the experiment. Methods. Acute ischemia was simulated in rabbits (n = 20) with subsequent myocardial reperfusion. All animals were anesthetized and mechanically ventilated through a nasotracheal tube. The experiment included occlusion of the left coronary artery by its clamping with a ligature for 45 min with subsequent reperfusion for 120 min during CPB. All animals were divided into 2 equal groups: 10 rabbits received nitric oxide supply to the extracorporeal circulation line in a dose of 40 ppm throughout the entire CPB period (the main group); 10 rabbits made up the control group. The ratio of the infarction area to the risk area was determined, and the quantity and nature of ventricular arrhythmias were accessed. Results. It was established that nitric oxide supply through the extracorporeal circulation line during CPB had a pronounced infarct-limiting effect, the infarct area to the risk area ratio decreased by 15% as compared to the control group, р = 0.0002. There was also a significant antiarrhythmic effect. A lesser quantity of polytopic and polymorphic ventricular extrasystoles were observed in the main group during periods of ischemia and reperfusion (p = 0.003 and p = 0.012). A statistically significant decrease in the venoarterial gradient of the partial pressure of carbon dioxide in the main group was associated with an increase in the urine flow rate amounting to 1.4 [1.3; 1.5] ml/kg/h in the main group and 1.15 [1; 1.3] ml/kg/h in the control group, p = 0.013. Conclusion. The data obtained during the experiment demonstrate the presence of cardioprotective properties of nitric oxide delivered to the extracorporeal circulation line when simulating myocardial ischemic-reperfusion injury. These properties manifest themselves as a 15% decrease of the infarction zone-risk area ratio, a fewer number of arrhythmias and improvement of tissue perfusion during CPB. Intraoperative myocardial protection by nitric oxide in patients operated with CPB should be the object of further clinical research.Received 19 June 2017. Revised 9 October 2017. Accepted 15 October 2017.Funding: The study did not have sponsorship.Conflict of interest: Authors declare no conflict of interest.Author contributions: All the authors comply with 4 ICMJE authorship criteria and contributed equally at every stage of the study.Acknowledgement: The authors express their gratitude to Ekaterina S. Tokareva and Aleksandra A. Nenakhova for support in preparation of the article.