Characterizing the Cardioprotective Phenotype of Brown Norway Rats: Importance of Optimal Ischemia Duration

The degree of cardiac ischemia‐reperfusion (IR) injury in Brown Norway (BN) and Dahl Salt Sensitive (SS) rats is remarkably different, with BN hearts being more resistant to IR injury than SS [1]. The objective of our study was to determine the role of varying ischemic duration on genome‐dependent cardioprotection in these two inbred rat strains. Langendorff‐prepared hearts from eight week old male BN and SS rats were perfused at constant pressure (90 mmHg) at 37ºC with crystalloid buffer solution. Isovolumetric left ventricular pressure, heart rate and coronary flow were measured before, during and after 25, 30 or 35 min of global no‐flow ischemia, and infarct size was determined at 120 min reperfusion. We found that longer ischemic periods were associated with worse functional recovery and larger infarct size by the end of reperfusion in both strains. However, the genetic background differentially modified this relationship such that optimal distinction between BN and SS strongly depended on ischemia time. These data suggest that differences in IR injury with varying ischemia duration affect the ability to investigate genome‐dependent cardioprotective pathways. Therefore, the choice of an optimal ischemia time [2] plays a crucial role during investigation of myocardial IR injury using this genetic model.