Change in surface charge density and membrane potential of intact mitochondria during energization

Abstract

Application of respiratory chain substrates or ATP to mitochondria leads to the so-called ‘energized state’. Various phenomena such as change in morphology [I ,2] , light scattering [3], redox states of respiratory chain components [4-61, or fluorescence of hydrqphobic probe such as 1-anilino-8-naphthalene sulfonate (ANS) [7-lo] have been observed during the energization. Here the surface charge densities of intact mitochondria determined by electrophoretic mobility, in energized or de-energized state, are reported. The negative charges appear when mitochondria are energized by substrates or ATP, and disappear when mitochondria are treated with respiratory inhibitors or uncouplers. It is shown, moreover, that the change in surface charge correlates with uptake of dibenzyldimethyl ammonium cation (DDA’), which is regarded as an indicator of membrane potential [ 111.