Effect of Mg2+ depletion of mitochondria on their permeability to K+: the mechanism by which ionophore A23187 increases K+ permeability.

Ionophore A23187 produces rapid swelling of rat liver mitochondria suspended in isotonio KNO₃ if an uncoupler and EDTA are also present. It also produces swelling of mitochondria in isotonic Mg(NO₃)₂ in the presence of an uncoupler. Washing with serum albumin removes the ionophore from mitochondria, as indicated by lack of swelling in magnesium nitrate (+ uncoupler). However, such treatment does not abolish rapid swelling in KNO₃ (+ uncoupler). This finding is interpreted in the sense that depletion of mitochondrial magnesium mobilizes K⁺/H⁺ antiport in the inner mitochondrial membrane.