Cardiac levels of fibronectin, laminin, isomyosins, and cytochrome c oxidase of weanling rats are more vulnerable to copper deficiency than those of postweanling rats.

The relative quantities of cardiac laminin, fibronectin, cytochrome c oxidase (CCO), and isomyosin types were studied by gel electrophoresis in male rats fed copper-deficient diets beginning either from the time of weaning for 5 weeks or from 5 weeks postweaning for 6 weeks with one group of copper-repleted rats. Increased levels of fibronectin and V(3) isomyosin but decreased levels of CCO subunit IV and laminin were found in weanling copper-depleted rats. In contrast, postweanling copper-depleted rats exhibited only increased levels of fibronectin and decreased levels of cardiac CCO subunit IV. Repletion of copper-deficient rats for 6 weeks was not sufficient to restore CCO subunit IV to the same level as controls. These results confirm that biochemical lesions in the basal laminae are a result of copper restriction. The decreased nuclear encoded subunits of CCO may help explain some of the mitochondrial pathology observed in dietary copper restriction. Increased V(3) isomyosin levels with low ATPase activity may help to conserve to a limited extent the ATP levels in copper-deficient cardiac tissue. These protein changes are consistent with the known morphological alterations of hearts from copper-restricted rats.