The Intensity of Free Radical Processes on Rat Liver Mitochondria under Moderate Hypothermia of Various Duration

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Moderate artificial hypothermia is widely used in clinical practice to protect organs from the effects of ischemia (reperfusion), trauma, and hypoxia. However, a decrease in the body temperature of homeothermic animals induces oxidative stress, the severity of which may depend on the time of exposure to the cold factor. Since mitochondria play a key role in the generation of reactive oxygen species, we studied the dependence of the intensity of free radical processes in rat liver mitochondria on the duration of moderate hypothermia (30°C). It turned out that short-term (30 min) hypothermia activates the processes of lipid peroxidation (POL), while the concentration of lipid hydroperoxides, Schiff bases, and malondialdehyde significantly increases. Prolongation of hypothermia to 1 h reduces the content of many lipid peroxidation products, and their normalization is observed with 3-h hypothermia. Short-term hypothermia and its prolongation up to 1 h is accompanied by oxidative destruction of mitochondrial proteins, which is manifested in a decrease in the content of sulfhydryl groups in them and an increase in carbonyl groups. At the same time, 3-h hypothermia contributes to the normalization of the studied markers of protein oxidative modification. The dynamics of changes in the levels of sulfhydryl and carbonyl groups in the mitochondrial matrix proteins is more pronounced in comparison with membrane proteins. The study of the spectral characteristics of mitochondrial membrane proteins showed a decrease in the intensity of their fluorescence at the initial stages of hypothermia. Tryptophan residues localized at the periphery make the main contribution to it. Prolongation of hypothermia up to 3 h contributes to restoration of fluorescence parameters to the control level. The data obtained in the analysis of the second derivative fluorescence spectra indicate changes in the spatial configuration of membrane proteins.