Effects of some antiarrhythmic agents on dog heart mitochondrial oxidative phosphorylation

Significant decreases in state 3 oxygen consumption, respiratory control index (RCI), ADP : O ratio and phosphorylation rate were observed in the presence of 0.1-1.0 mM quinidine; 0.5 mM or greater concentrations elevated state 4 oxygen consumption. Lidocaine (1-2.5 mM) also depressed RCI and increased state 4 oxygen consumption but procaine amide (1-2.5 mM) was without effect. It is suggested that cardiodepression by quinidine may be associated with its ability to impair mitochondrial metabolism.