Effect of Catecholamines and Adrenergic Blocking Agents on Oxidative Phosphorylation in Rat Heart Mitochondria

Abstract

Polarographic methods were used to examine oxidative phosphorylation in mitochondria isolated from hearts of rats treated with 5 mg/kg epinephrine, norepinephrine, or isoproterenol in oil given subcutaneously. Uncoupling of oxidative phosphorylation occurred (P/O ratio 2.1 ± .04 compared to P/O ratio of controls, 2.9 ± .03). Other indices of mitochondrial function, including oxygen consumption, respiratory control, adenosinetriphosphatase activity, and swelling were normal. The time course of depression of P/O ratio was parallel to that of myocardial catecholamine uptake, yet normal mitochondria were not affected by catecholamines in vitro (10 -3 M). Adrenergic blocking agents in vitro did not improve the function of mitochondria from catecholamine-treated animals. No free fatty acids were detectable in extracts of mitochondria from either group by gas liquid chromatography, and the lipid profiles of extracts from each were similar by thin layer chromatography. The data indicate a means by which large quantities of exogenous or endogenous catecholamines could lead to increased oxygen consumption in vivo, or contribute to impairment of myocardial function.