Isolated heart function during ischemia and reperfusion in sucrose-fed rats: effect of insulin infusion

In myocardial damage due to ischemia-reperfusion, the administration of insulin together with glucose and potassium may be protective, although in some patients and animal models, it is ineffective. In a rat model (HTG) with characteristics of the metabolic syndrome, induced by sucrose feeding, ischemia-reperfusion of the isolated heart evidences a less favorable outcome than in control animals, particularly males. We investigated the effect of insulin infusion during the reperfusion period in isolated hearts from control and HTG male and female rats. Weanling Wistar rats were given commercial rat chow and tap water (C rats) or 30% sucrose solution (HTG rats) for 8 months. They developed moderate hypertension and hyperinsulinemia, central adiposity, nephropathy, and hypertriglyceridemia. Cardiac function was recorded in a Langendorff preparation subjected to 25 min ischemia and 15 min reperfusion. The handicapped functionality of HTG hearts is more apparent under conditions of stress. Insulin administration improved particularly mechanical work and +dp/dt max variables. The effect of sex was observed on the type of arrhythmias developed during reperfusion: Only the males showed lethal ventricular fibrillation, which disappeared after insulin administration. Females had lower levels of cardiac enzymes creatine kinase (CKMB) and lactic dehydrogenase (LDH), but their performance was not hindered, probably on account of protective factors such as estrogens. Summing up, the pathological features of the HTG model did not prevent insulin from exerting some of its beneficial effects in HTG hearts. Sex differences in the outcome were more apparent in the type of arrhythmias after reperfusion; they were lethal in HTG males only, but insulin prevented their onset.