Water electrolyte concentrations in different segments of the kidney of rats during prolonged restriction of motor activity.

The objective of this investigation was to determine the electrolyte concentration in plasma and in different segments of the kidney and kidney structural changes during a 90-day restriction of motor activity (hypokinesis). The studies were performed on 120 male Wistar rats divided into two groups. The first group was placed under ordinary vivarium conditions (vivarium control animals) and the second group subjected to hypokinesia (hypokinetic animals). The hypokinetic effect was carried out by keeping the rats in small individual wooden cages which restricted their movements without hindering food and water intake. Determinations were made of the concentration of sodium and potassium in plasma and in the renal cortex, external medullary layer and papilla. The concentration of electrolytes increased in the plasma while in the different segments of the kidney--primarily in the wet cortical and medullary matter--it decreased significantly compared with the control animals. Microdissection of the kidney of rats also demonstrated significant structural differences in nephrons of the hypokinetic animals when compared with the controls. Prolonged restriction of motor activity induces significant changes in the structure of the nephrons and in the electrolyte concentration of the plasma and different segments of the kidney.