The cardioprotective hibernator phenotype. Winter (hibernating [HIB]) and summer active (SA) arctic ground squirrels (AGSs) exhibit reduced myocardial injury after ischemia–reperfusion (I/R) compared to Brown Norway (BN) or Dahl salt-sensitive (SS) rats, as evidenced by reduced plasma markers of myonecrosis at both the 3-h (R3h) and 24-h (R24h) reperfusion time points (#P < 0.01, *P < 0.05 by ANOVA with Tukey post hoc correction; A). Winter (HIB) AGS further demonstrated preserved echocardiographic left ventricular systolic function (LV-FAC) after I/R compared to SA AGS or rats (*P < 0.05, ANOVA with Tukey post hoc correction; B) and reduced myocardial apoptosis as evidenced by terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) staining (C) corroborated by cleaved caspase-3 levels (D) at the 3-h reperfusion time point (*P < 0.05, Mann–Whitney U test). Data are presented as mean ± SD, N = 8/group.