Sodium loss with tissue sodium deficiency in sodium supplemented and unsupplemented rats during prolonged hypokinesia.

To demonstrate the effect of sodium supplementation and hypokinesia (HK; diminished movement) on the total bodily sodium (Na+) loss and tissue Na+ deficiency, tissue Na+ content, plasma Na+ level and Na+ loss were measured. Studies were conducted on male Wistar rats during a pre-experimental and experimental period. Animals were equally divided into four groups: unsupplemented vivarium control rats (UVCR), unsupplemented hypokinetic rats (UHKR), supplemented vivarium control rats (SVCR) and supplemented hypokinetic rats (SHKR). A daily supplementation of 3.50 mEq sodium chloride (NaCl) was given to animals in the SVCR and SHKR groups. Gastrocnemius muscle and right femur bone Na+ level decreased (p<0.05), and plasma Na+ level and urine and fecal Na+ loss increased (p<0.05) in the SHKR and UHKR groups compared to their pre-experimental values and the values in their respective vivarium control groups (SVCR and UVCR). Muscle and bone Na+ content decreased more (p<0.05), and plasma Na+ level and urine and fecal Na+ loss increased more (p<0.05) in the SHKR group than in the UHKR group. It is concluded that tissue Na+ deficiency during HK is more evident when Na+ intake is higher and that the total bodily Na+ loss exacerbated more with higher than lower tissue Na+ deficiency. This shows that tissue Na+ deficiency is not the result of the lower Na+ content in the food consumed and that the total bodily Na+ loss is not caused by the higher tissue Na+ content but due to the impossibility of the body to use Na+ when animals are submitted to prolonged HK.