Chronic ethanol ingestion increases efficiency of oxidative phosphorylation in rat liver mitochondria

The efficiency of oxidative phosphorylation was compared between rats chron ically fed with ethanol and controls. (i) Results showed that the liver mit ochondria state 4 respiratory rate was strongly inhibited, while the corres ponding protonmotive force was not affected; (ii) the cytochrome oxidase co ntent and activity were decreased and (iii) the oxidative-phosphorylation y ield was increased in the ethanol exposed group. Furthermore, oxidative pho sphorylation at coupling site II was not affected by ethanol, Cytochrome ox idase inhibition by sodium-azide mimicked the effects of ethanol intoxicati on in control mitochondria. This indicates that the decrease in cytochrome oxidase activity induced by ethanol intoxication directly increases the eff iciency of oxidative phosphorylation. (C) 2000 Federation of European Bioch emical Societies.