EFFECTS OF MAGNESIUM-DEFICIENCY ON STRENGTH, MASS, AND COMPOSITION OFRAT FEMUR

Magnesium(Mg) participates in the normal formation and remodeling of b one. However, little is known about effects of Mg status on the biomec hanical function of bone. We examined gross morphometry and compositio n as well as biomechanical properties of the femurs of male rats fed d iets adequate or deficient in Mg. Comparison of deficient animals and controls yielded a number of differences (all significant at P < 0.05) . Mg-depleted animals exhibited slow growth, inefficient food utilizat ion, and greatly reduced concentrations of Mg in both serum and femur ash. Compared with controls, femurs from depleted animals were shorter , but wet weights, diameters, and midfemoral cross-sectional areas sho wed no differences. Bone length was reduced to a greater degree than c ould be accounted for by differences in body weights between the group s. Bones of Mg-deficient rats contained less dry matter and less ash ( which contained more Ca/g) than those of controls, along with a higher percentage of moisture. Significantly reduced bone strength in deplet ed animals was evident from the lighter loads supported at the elastic limit (yield point) and at fracture and from decreased stresses accom panying those loads. Modulus of elasticity, however, was not affected by Mg depletion. Different yield and breaking loads were related to di fferent body weights of groups, but stresses were reduced for deficien t bones even after adjusting for body size. Our data establish abnorma l biomechanical behavior of cortical bone in Mg-deficient animals and emphasize the importance of measuring such functional properties of bo ne in the assessment of responses to altered metabolic conditions unde r experimental conditions.