Preserved Mitochondrial Calcium Retention Capacity In Summer-Active Arctic Ground Squirrels Undergoing Normothermic Myocardial Ischemia/Reperfusion Injury

Arctic Ground Squirrels (AGS) exhibit a high degree of endogenous resistance against myocardial ischemia/reperfusion (IR) injury compared to the best protected rat strain (Brown Norway, BN). We tested if this species-specific myocardial protection is associated with increased mitochondrial calcium retention capacity (CRC). Isolated hearts from BN (n=15) and summer-active AGS (n=11) underwent 45 min global cardioplegic ischemia and 60 min reperfusion with Krebs solution containing 7.5 mM glucose or 1% Intralipid in addition. Left ventricular pressure was measured isovolumetrically. Cardiac mitochondria were isolated and CRC was measured by spectrofluorometry of calcium green at 503/532 nm excitation/emission for complex I and II substrates in response to intermittent calcium boluses. While multiple regression analysis revealed intralipid, female gender and species (AGS) as predictors of better myocardial function following IR, predictors of improved CRC were AGS and mitochondrial substrate only. These resu...