[Adrenaline activates oxidative phosphorylation of rat liver mitochondria through alpha 1-receptors]

We studied the effects and mode of action of epinephrine on the oxidative phosphorylation of rat liver mitochondria. With either succinate or beta-hydroxybutyrate as substrate, i.v. injection of 1.5 microgram/100 g epinephrine increased the respiratory rates by 30-40% in state 3 (with ADP), and by 20-30% in state 4 (after ADP phosphorylation), so that the respiratory control ratio (state 3/state 4) changed little. The respiratory stimulation by epinephrine was maximal 20 minutes after its injection. The action of epinephrine on mitochondria was blocked by pretreatment of the animals with the alpha 1-antagonist prazosin but not by treatment with the beta-antagonist propranolol. I. v. injection of 10 micrograms/100 g phenylephrine evoked the same mitochondrial response as epinephrine. I. v. administration of 50 micrograms/100 g dibutyryl cyclic AMP enhanced glycaemia but did not affect mitochondrial respiration. Epinephrine therefore has an alpha 1-type of action on mitochondrial oxidative phosphorylation.