Effects of Suspension Hypokinesia/Hypodynamia on Ca Metabolism of Rats Fed with Various Protein Concentrations

Hypokinesia/hypodynamia was induced in the hindlimbs of rats by a suspension harness, and metabolic balance studies, especially regarding calcium, were done. During a 10-day period of hypokinesia, the calcium concentration in the serum was not significantly altered with the exception of 5% casein diet, while the serum inorganic phosphorus concentration of hypokinetic rats was significantly decreased independent of the various dietary protein concentrations. Calcium balance in the suspended rats was significantly decreased, especially with the high protein diet, but the total calcium balance for 10 days was positive. The activity of alkaline phosphatase and the concentration of desoxyribonucleic acid (DNA) in the femoral diaphysis were markedly decreased by the suspension. These results demonstrate that the hypokinesia/hypodynamia by the suspension harness can induce a disorder of bone metabolism, and may be useful for studying the changes in bone metabolism caused by simulated weightlessness.