Energy coupling in liver mitochondria from dystrophic mice: differential sensitivity of oxidative phosphorylation and Ca2+ uptake to K+.

Studies were carried out to examine oxidative phosphorylation, cation uptake, and electrokinetic properties of liver mitochondria from genetically dystrophic mice in comparison with those from livers of littermate controls. While no differences were seen with respect to the rates of substrate oxidation, ADP/oxygen ratio, and RCl and cytochrome content, the mitochondria from the dystropic group were characterized by an elevated basal ATPase activity in the presence of NaCl. Additionally, these mitochondria were highly sensitive to high concentrations of exogenously added K+ that, besides stimulating state 4 respiration, caused uncoupling in the mitochondria. These mitochondria accumulated Ca2+ at a higher rate, and unlike the controls, Ca2+ uptake was not sensitive to exogenously added K+. It was also observed that the net negative charge on mitochondria decreased significantly in the dystrophic state. It is thus apparent that muscular dystrophy manifests itself also in terms of alteration in the membrane properties of liver mitochondria.