Ultrastructural and biochemical studies of the brain and other organs in rat after chronic ethanol administration. III. Influence of ethanol intoxication on oxidative phosphorylation of the rat brain mitochondria with ultrastructural and morphometric evaluation of mitochondrial fraction).

The effect of chronic ethanol intoxication on oxidative phosphorylation in the rat brain mitochondrial fraction was examined. Moreover, electron microscopy was used to verify the quantitative composition of the fraction and for examination of ultrastructural changes in the mitochondria. The experiments were carried out with 60 rats receiving, beside the normal diet, ethyl alcohol according to a modified RATCLIFFE model. In isolated rat brain mitochondria the NAD-dependent oxidation of substrates (glutamate + malate) was decreased. The phosphorylation index ADP/0 and the respiratory control ratio (RCR) in rat brain mitochondria from ethanol-treated rats were unchanged in the presence of both succinate and glutamate + malate. Chronic ethanol feeding did not induce any changes of succinate dehydrogenase and cytochrome oxidase activities in solubilised mitochondria fractions of rat brain. Electron microscopy studies revealed that mitochondria from control animals retained their outer and inner membranes, whereas those from rats given ethanol were almost always swollen and some were disrupted. In mitochondrial fractions isolated from ethanol-intoxicated rats an increase was observed of contaminating elements i.e. axons and synaptosomes of various sizes. It should be stressed that the mitochondria located inside synaptosomes and axons were unchanged. The composition of the fractions was quantitatively evaluated and confirmed the diminution of "free" mitochondria in the experimental fractions in favour of "bound" mitochondria which mainly occurred in the synaptosomes with preserved metabolic activity. On the basis of electron microscopy studies it could be suggested that ethanol intoxication causes the damage of some mitochondria, which become more sensitive to mechanical destruction during isolation procedure, and they do not sediment together with the fraction of normal ones. The absence of "free" mitochondria in pellets explains the spurious lack of disturbances in the energy metabolism of brain mitochondria after chronic ethanol intoxication.