Valinomycin-induced chloride permeability in isolated rat liver mitochondria

1. Ionophore-induced osmotic swelling was used to study Cl- transport in isolated rat liver mitochondria. 2. Energy-dependent, neutral ionophore-induced swelling in Cl- salts at pH 7.2 required K+ and was preceded by a brief lag phase that was absent in chlorotributyltin-induced swelling. 3. Treatments that stimulated or inhibited mitochondrial K+/H+ exchange had qualitatively similar effects on both valinomycin-induced swelling and the associated lag phase. 4. The results suggest that valinomycin-induced Cl- permeability results from an interaction between the K+/H+ antiporter and neutral ionophore K+ complexes.