Activity of cytosolic isoenzymes of endogenous aldehydes catabolism under the conditions of acetaminophen-induced hepatitis on the background of protein deficiency

The research deals with the determination of the activity of aldehyde dehydrogenase (EC 1.2.1.3), aldehyde reductase (EC 1.1.1.21), the content of TBA-active products and protein carbonyl derivatives in the rat liver cytosolic fraction under the conditions of acetaminophen-induced hepatitis and alimentary deprivation of protein. The researches were conducted on white rats of 90-100 g body mass aged 2-2.5 months. There were used 36 rats, which according to the experimental model were separated into 4 groups: I – animals receiving full-value semi-synthetic ration (C); II – animals receiving low-protein ration (LPR); III – animals with acetaminophen-induced liver injury receiving complete ration (H); IV – animals with acetaminophen-induced liver injury that were previously maintained on semi-synthetic low-protein ration (LPR+H). The acetaminophen-induced liver injury was modeled by per os administration of 2% starch suspension of acetaminophen in daily dose 1250 mg/kg (0,5 LD50) of the body weight. Cytosolic fraction was obtained by differential centrifugation at the temperature 0-3 0С in the solution which contained sucrose, EDTA and tris-HCl buffer. Aldehyde dehydrogenase and aldehyde reductase activities were determined spectrophotometrically by the tempo of regeneration of NAD+ and oxidation of NADH respectively. Enzymatic activity was calculated using the molar extinction coefficient of according nicotinamide coenzymes. The concentration of TBA-active products was assessed by the reaction with thiobarbituric acid and forming the colored complex. The level of the oxidative protein modification assessed via amount of 2.4-dinitrophenylhydrazone derivatives, produced in reactions of oxidized amino acid residues with 2.4-dinitrophenylhydrazine. The most pronounced decrease in the activity of enzymes utilizing endogenous aldehydes is observed in the liver cytosolic fraction of animals with toxic liver injury maintained under the conditions of alimentary protein deficiency. The established fact is explained as by the disturbances of enzyme structural-functional organization and its synthesis, as by changes of the ratio between redox forms of the nicotinamide coenzymes. Meanwhile, the accumulation of TBA-active products and protein carbonyl-derivates in the liver cytosolic fraction of animals of this experimental group was established. In this case, a statistically significance of a difference between the concentration of these products in protein-deficient and control rats under the current experimental conditions was not detected. The accumulation of aldehyde products of lipid and protein oxidative damage on the background of the reduction in the activity of enzymes providing aldehyde catabolism may be considered as a possible mechanism underling hepatocyte dysfunction under the conditions of toxic damage in protein-deficient animals.