Responses of Myocardial Antioxidant Systems to Intermittent Hypoxia and Ethanol Withdrawal

Schulz, Diana R., Responses of Myocardial Antioxidant Systems to Intermittent Hypoxia and Ethanol Withdrawal. Master of Science, May 2008, 50 pp., 3 tables, 14 figures, bibliography: 38 titles. Introduction: The effects of ethanol intoxication on the heart have been extensively studied over the past century; however the consequences of ethanol withdrawal on the heart have not been documented. Myocardial adaptations to hypoxia can improve contractility, enhance antioxidant defense mechanisms, decrease lipid peroxidation induced by oxidative stress, and bolster cardiac resistance to ischemia-reperfusion. This study was conducted to determine if ethanol intoxication-withdrawal can harm the myocardium, and if intermittent hypoxia conditioning (IHC) can induce antioxidant enzymes and proteins that blunt these effects. Hypothesis: IHC increases myocardial antioxidant enzymes and other stress proteins, which could protect myocardium from ethanol intoxication-withdrawal. Methods: Four month old Sprague Dawley rats (n=61) were divided into 8 groups. Four groups were fed a 6.4% ethanol enriched diet, and the other four were fed an isocaloric dextrin diet. IHC was initiated two weeks after the diets began. The antioxidant N-acetylcysteine (NAC) was injected throughout the IHC and sham conditioning programs to interrogate the role of reactive oxygen species in the effects of ethanol intoxication-withdrawal and IHC on myocardial proteins. Proteins were extracted from snap-frozen myocardium for assays of nitric oxide synthase (NOS), gluthathione peroxidase (GPx) and superoxide dimustase (SOD) activities, and immunoblot analyses of endothelial NOS (eNOS) and heat shock protein 70 (Hsp70). Results: Ethanol withdrawal inactivated myocardial SOD, but did not affect activities of GPx and NOS, or contents of Hsp70 and eNOS. IHC lowered SOD activity by 55% in dextrin-fed rats, but partially protected SOD activity from ethanol intoxication-withdrawal. IHC did not affect myocardial GPx, NOS, and Hsp70 in dextrin and ethanol-withdrawn rats. NAC alone increased SOD activity in dextrin-fed and ethanol withdrawn rats and, when combined with IHC, NAC fully protected SOD activity from ethanol intoxication-withdrawal. Conclusions: Ethanol intoxication-withdrawal had statistically significant effects on the antioxidant enzyme SOD. IHC and NAC selectively protected SOD activity from ethanol intoxication-withdrawal. This specificity suggests that the oxidative stress induced by ethanol intoxication-withdrawal is discrete in comparison to the massive oxidative stress inflicted on the brain under these conditions. The differences in the intensity of oxidative stress could be one of the factors influencing the divergence of results in comparison to previous investigations of ethanol intoxication-withdrawal.