IMPAIRED MECHANICAL STRENGTH OF BONE IN EXPERIMENTAL COPPER DEFICIENCY

Copper, through its role as cofactor for lysyl oxidase, is essential f or intra- and inter-molecular cross-links in collagen. Copper deficien cy, in man and in animals, is associated with bone fragility ascribed to defective cross-links. To assess bone strength in copper-deficient animals, we designed a sensitive torsion-testing apparatus according t o biomechanical considerations. Femora from 7 copper-deficient rats an d from their pair-fed controls were tested in torsional loading until fracture. Significant decreases in the maximal sustained torque (t = 2 .93, p < 0.05), in the ultimate angular deformation (t = 2.52, p < 0.0 5) and in the toughness (t = 2.88, p < 0.05) were demonstrated. In a c omplementary study, it was shown that the ash weight and the calcium c ontent of the femora from the copper-deficient animals did not differ from those of the controls. It was likely, therefore, that the impaire d mechanical strength was related to defects in the collagen component of bone.