Rat liver mitochondria impairments under acute carbon tetrachloride-induced intoxication. Effects of melatonin

The aim of the present work was to investigate the mechanisms of oxidative damage of rat liver mitochondria in vitro, under hypochlorous acid (HOCl)-induced oxidative stress, and in vivo, under acute carbon tetrachloride-induced intoxication in rats. Hypochlorous acid (50–300 μM), the main inflammatory agent, inhibited liver mitochondria respiratory activity and caused uncoupling in the respiratory and phos-porylation processes. The toxic damage of rat liver after 24 h of acute carbon tetrachloride-induced intoxication (4 g/kg, intragastrically) was accompanied by a significant reduction in succinate- and glutamate-dependent respiration rate in state 3 (by 65%, p < 0.001, and by 50%, p < 0.01, respectively). The respiration control ratio approached 1, reflecting the loss of respiration control. The phosphorylation coefficient significantly decreased due to uncoupling of the oxidation and phosphorylation processes. The mitochondrial alterations were associated with oxidation of intramitochondrial GSH by 25% (p < 0.05), the marked inhibition of succinate dehydrogenase (complex II) by 35% (p < 0.05), and the rise of blood plasma nitric oxide level by 45% (p < 0.05). The impairment of mitochondrial respiratory function may result from the inhibition of enzymatic activities in the respiratory chain and the damage of mitochondrial membrane during intoxication and plays a key role in the development of the CCl₄-induced hepatotoxicity. Melatonin administration under CCl₄-induced intoxication (three times at a dose of 10 mg/kg) increased the rate of succinate oxidation in state 3 by 30% (p < 0.05) and reversed the increase in glutathione peroxidase activity. Melatonin prevented an elevation of nitric oxide level in the blood plasma of intoxicated animals but did not protect mitochondrial functions under acute intoxication.