Distribution of calcium in central nervous system tissues and bones of rats maintained on calcium-deficient diets

Current changing epidemiological pattern in the Western Pacific area suggests a contribution of the environmental factors to the pathogenetic process of amyotrophic lateral sclerosis (ALS). The condition of unbalanced mineral levels found in the soil and drinking water samples from the ALS foci showing low content of calcium (Ca) and magnesium (Mg) plus high content of aluminum (Al) was experimentally mimicked in this study using rats. In the groups fed low Ca, low Ca-Mg, and low Ca-Mg plus high Al diets, serum Ca levels were lower than that in the group fed the standard diet. Ca content of CNS tissues showed higher values in the unbalanced diet groups, especially in the spinal cord of low Ca-Mg plus high Al diet group, than those in the standard diet group, determined by inductively-coupled plasma emission spectrometry (ICP). Ca content in heart, liver, kidney, and abdominal aorta in groups fed low Ca-Mg, and low Ca-Mg plus high Al diets was higher than that in low Ca, and standard group. Ca content in muscle in the three unbalanced diet groups was significantly higher than in the standard diet group. Ca and Mg contents in lumbar spine and cortical bone showed lower values in the unbalanced diet groups than those values in the standard diet group. These findings suggest that under the condition of derangement of bone mineralization induced by unbalanced mineral diets fed to the experimental rats, Ca and Mg may be mobilized from bone, keeping their content in soft tissues, including CNS tissue, for utilization of vital activities, thereby resulting in a deposition of Ca while maintaining an almost normal value of magnesium in the CNS tissues.