Effect of reducing agents and uncouplers on the electrical potential generated by mitochondrial ATPase activity

Beef heart submitochondrial particles bound to phospholipids impregnated filters generated an electrical potential upon the addition of ATP. The magnitude of the electrical potential reached depended on the phospholipid mixture composition used for filter impregnation, phosphatidylethanolamine being the active component for the electrical potential generation. Uncoupler FCCP (p-trifluoromethoxy carbonyl cyanide phenylhydrazone) inhibited the transmembrane electrical potential generation by diminishing the electrical resistance of the system as a result of its protonophoric action. However, uncouplers 2, 4-dinitrophenol and dicoumarol did not provoke large modifications of the electrical resistance under the conditions of pH and concentration used, and their action varied with the time elapsed after the submitochondrial particles purification, favouring the idea of the uncoupler interaction with a specific site on the membrane. Addition of sodium dithionite resulted in a higher plateau value for the electrical potential consistent with the promoted increase in ATPase activity. The effect of this agent was reversed by the 2,6-dichlorophenol-indophenol added at equivalent concentrations.