Abstract： AIM:To observe the protective effects of urethane plus HTK on the isolated rat hearts in prolonged hypothermic preservation.METHODS:Male Sprague-Dawley rats(250-280 g)were divided into 2 groups(n=6 per group)according to each preservation solution used:control group,HTK solution;experimental group,HTK solution plus urethane.The hearts were arrested and stored in each preservation solutions respectively for 6 and 18 h at 4℃.After preservation,the myocardial function,ATP content,cardiomyocyte apoptosis and uhrastrueture were examined.RESULTS:Compared with control group,experimental group showed higher reeovery of cardiac.function,lower rate of cardiomyocyte apoptosis and better cardiomyocyte uhrastructure both for 6 and 18 h of preservation.The ATP content after 18 h of preservation in control group was significantly higher than that in experimental group.CONCLUSION:Urethane led to significandy better and longer preservation in isolated hearts subjected to prolonged hypothermic preservation.