Anilinonaphthalenesulfonate fluorescence changes induced by non-enzymatic generation of membrane potential in mitochondria and submitochondrial particles

Changes in the fluorescence of 1-anilino-8-naphthalenesulfonate (ANS⁻) accompanying non-enzymatic generation of the membrane potential in mitochondria and sonicated submitochondrial particles have been demonstrated. Generation of the membrane potential was induced by addition of an ionophore (valinomycin for K⁺, or tetrachlorotri-fluoromethylbenzimidazole for H⁺) under conditions where there existed K⁺ (or H⁺) gradients across the mitochondrial membrane. The ANS⁻ fluorescence decreased when the mitochondrial (or particle) interior became more negative, and increased when it became more positive. Collapse of the membrane potential reversed the ANS⁻ responses. A hypothesis is put forward to explain the energy-dependent ANS⁻ responses in mitochondria and particles by the membrane potential-induced redistribution of ANS⁻ between the membrane and water phases.