Electrolyte and water contents in organs and tissues of rats during and after exposure to prolonged restriction of motor activity.

Sodium and potassium concentrations in organs and tissues of rats have been determined during hypokinesia (HK) and posthypokinesia (post-HK) periods. The study was performed on 180 male Wistar rats with an initial body weight of 370 to 390 g. They were divided into control and experimental groups: the 1st group of rats was placed under ordinary vivarium conditions (control) and the 2nd group was subjected to 90 days of HK (hypokinetic animals). The animals were kept in small individual wooden cages which restricted their movements in all directions without hindering feed and water intake. On the 30th, 60th and 90th day of the HK period and on the 5th, 10th and 15th day of the post-HK period animals were decapitated, and potassium and sodium concentrations were measured in the myocardium, skeletal muscles, erythrocytes and plasma. Fluid content was also determined in the myocardium and skeletal muscles. During both the HK period and initial stages of the post-HK period the concentration of sodium and potassium in the myocardium, skeletal muscle, plasma and erythrocytes as well as water content in the myocardium and skeletal muscle changed significantly.