Studies on the effects of copper deficiency on rat liver mitochondria. I. Changes in mitochondrial composition

As part of an investigation of the lesions of copper (Cu) deficiency a study was undertaken of the copper, iron, cytochrome and fatty acid composition of liver mitochondria from Cu deficient and Cu-adequate control rats. Cu concentrations were significantly decreased in whole liver, liver mitochondria and in blood plasma. Total iron was significantly increased in whole liver but remained at the normal level in mitochondria. Cytochrome c oxidase (EC 1.9.3.1) and its component cytochromes a and a3 were significantly reduced in liver mitochondria from Cu-deficient rats, whereas there was no effect on the concentration of cytochromes b, c1 and c. Evidence from comparisons between cytochrome c oxidase activity and the amount of enzyme present, as assessed from the mitochondrial cytochrome a and a3 content, suggests that in addition to an absolute loss of enzyme, Cu-deficiency adversely affects the efficiency of the residual enzyme. Severe Cu deficiency had no effect on 'ageing' or 'swelling' properties of liver mitochondria, indicating no marked effects on fatty acid composition. Fatty acid analyses demonstrated a slight but significant increase in docosapentenoic acid (22:5) of Cu-deficient mitochondria, but since this represents a minor component there was no change observed in the 'unsaturation index'. It was concluded that, in contrast to previous reports, Cu deficiency of the severity reported did not have a deleterious effect on the integrity and permeability of the inner mitochondrial membrane as exemplified by any qualitative modification of fatty acid constitution per se.