Cardioprotective effect of chronic low dose ethanol drinking: Insights into the concept of ethanol preconditioning

The reason why low-to-moderate alcohol drinking is associated with reduced cardiovascular mortality is not elucidated. While data suggested that ethanol drinking may have a protective effect on global cardiac ischemia, the effect of chronic low dose ethanol drinking (CLEthD) on myocardial infarct size has not been evaluated in a model of regional ischemia. Using an isolated rat heart model to exclude the effect of various in vivo confounders, we have studied the effect of CLEthD on infarct size (IS) and left ventricular function after 30 min of regional ischemia and 120 min of reperfusion. The effect of CLEthD was compared with ischemic preconditioning (IPC) and protein kinase C (PKC) isoforms were analysed in the myocardium before the 30-min ischemia. Ethanol-fed rats received 9% (v/v) ethanol in their drinking water for 7 weeks. Four groups of rats were studied: (1) control, (2) ethanol, (3) control + IPC, (4) ethanol + IPC. Compared with controls (59 ± 10), IS (as percent of risk zone) was smaller in the ethanol (39 ± 6) and IPC (31 ± 8) groups (both p < 0.05). Combination of ethanol and IPC in the same rats further decreased IS (-46% vs. ethanol, p < 0.05). PKC analyses did not show sustained ε isoform translocation in that model. These data indicate that chronic low dose ethanol drinking actually induces in the rat heart a chronic protective state that is independent from an effect on the traditional (lipid and coagulation) risk factors. Further studies are required to elucidate the mechanisms of that protection.