Reactive free radical generation in vivo in heart and liver of ethanol-fed rats: correlation with radical formation in vitro.

Abstract

Rats fed a high-fat ethanol-containing diet for 2 weeks were found to generate free radicals in liver and heart in vivo. The radicals are believed to be carbon-centered radicals, were detected by administering spin-trapping agents to the rats, and were characterized by electron paramagnetic resonance spectroscopy. The radicals in the liver were demonstrated to be localized in the endoplasmic reticulum. Rats fed ethanol in a low-fat diet showed significantly less free radical generation. Control animals given isocaloric diets without ethanol showed no evidence of free radicals in liver and heart. When liver microsomes prepared from rats fed the high-fat ethanol diet were incubated in a system containing ethanol, NADPH, and a spin-trapping agent, the generation of 1-hydroxyethyl radicals was observed. The latter was verified by using "3C-substituted ethanol. Microsomes from animals fed the high-fat ethanol-containing diet had higher levels of cytochrome P-450 than microsomes from rats fed the low-fat ethanol-containing diet. The results suggest that the consumption of ethanol results in the production of free radicals in rat liver and heart in vivo that appear to initiate lipid peroxidation.Chronic excessive use of alcohol by humans results in liver disease (1, 2) characterized by fatty infiltration, which can lead to fibrotic degeneration and necrosis (1,3,4). However, the mechanisms leading to the development of alcoholic liver disease remain unclear. Lipid peroxidation was linked to ethanol consumption by Di Luzio and coworkers (5, 6), who reported that antioxidants prevented the development of fatty liver after a large acute dose of ethanol. Investigations by others have subsequently indicated that lipid peroxidation appears to occur in the livers of animals soon after the administration of an acute dose of alcohol. Much of the evidence for these claims has been based on the thiobarbituric acid assay for malondialdehyde in livers of animals treated with ethanol (7, 8), but increases in conjugated dienes and chemiluminescence as well as decreases in hepatic glutathione have also been reported (8). In addition, Muller and Sies (9) have reported an enhanced production of ethane and n-pentane, which are believed to be products of the peroxidative degradation of membrane lipids, during the metabolism of ethanol by perfused livers. These various findings have been interpreted as evidence that lipid peroxidation has occurred in the liver as a result of ethanol metabolism. Lipid peroxidation has also been proposed as a mechanism of ethanol-induced toxicity in the heart (10), gastric mucosa (11), and testes (12). However, the role of peroxidative events in the development of human alcoholrelated disease is highly controversial.Mechanisms that may initiate lipid peroxidation after ethanol exposure are also uncertain. Several laboratories have presented evidence that chronic ethanol feeding stimulates the production of hydroxyl radicals by liver microsomes (13,14). If this type of radical production occurs in the...

CYP2E1 and oxidative liver injury by alcohol

“…CYP2E1 can also promote the one electron oxidation of ethanol to the 1-hydroxyethyl radical. Detection of the 1-hydroxyethyl radical in the bile after administration of ethanol to rodents has been a most valuable assay for determining ethanol-induced radical formation and oxidant stress in vivo (26,59).…”

Direct evidence that oxygen-derived free radicals contribute to postischemic myocardial dysfunction in the intact dog.

“…Plasma specimens were analyzed by EPR spectroscopy as has been described (12,(16)(17)(18)(19). The spectrometer settings are specified in the legend to Fig.…”

Activation of nuclear factor kappa B and cytokine imbalance in experimental alcoholic liver disease in the rat

“…2,3,6,7 Lipid peroxides are also potentially hepatotoxic and increased levels are seen after alcohol administration. 8,9 A concerted effect of endotoxin and lipid peroxides in promoting liver injury probably occurs.…”