Relationship between ischaemic time and ischaemia/reperfusion injury in isolated Langendorff-perfused mouse hearts

Myocardial functional recovery and creatine kinase (CK) release following v arious periods of ischaemia were investigated in isolated mouse hearts. The hearts were perfused in the Langendorff mode with pyruvate-containing Kreb s-Hensleit (KH) buffer under a constant perfusion pressure of 80 mmHg, and were subjected to either continuous perfusion or to 5, 15, 20, 25, 30, 45 o r 60 min of global ischaemia followed by 45 min of reperfusion. In hearts s ubjected to ischaemic periods of 5, 15 or 20 min, there was a transient red uction in the left ventricular (LV) dP/dt max during the early phase of rep erfusion, while the recovery at the end of reperfusion reached a level simi lar to that in hearts subjected to continuous perfusion. In hearts subjecte d to longer ischaemic periods, i.e. 25, 30, 45 or 60 min, the decrease in t he cardiac performance was more pronounced and persistent, with significant ly lower recovery in LV dP/dt max and higher LV end diastolic pressure (LVE DP) at the end of reperfusion than in the non-ischaemic hearts. There were no significant differences in the recoveries in coronary flow or in heart r ate (HR) between groups. Similarly to the functional recovery, the release of CK showed a clear ischaemic length-related increase. In conclusion, the Langendorff-perfused isolated mouse heart could be a valuable model for stu dies of myocardial ischaemia/reperfusion injury. Future studies using gene- targeted mice would add valuable knowledge to the understanding of myocardi al ischaemia/reperfusion injury.