FLUID ELECTROLYTE CHANGES DURING PROLONGED RESTRICTION OF MOTOR-ACTIVITY IN RAT

Water and electrolyte changes in urine and plasma of rats during prolo nged restriction of motor activity (hypokinesia), have been studied, o n 90 male Wistar rats (375 to 396 g) during a 15 day period of prehypo kinesia and during a 90 day period of hypokinesia (HK). All rats were divided equally into two groups: rats placed under ordinary vivarium c onditions served as vivarium control rats (VCR) and rats subjected to HK served as hypokinetic rats (HKR). The hypokinetic effect was carrie d out by keeping the HKR group in small individual cages that restrict ed all their movements in all directions without hindering food and wa ter intake. During the 15 days of the prehypokinetic period and during the 90 days of the hypokinetic period, fluid consumed and eliminated in urine, food intake, body weight, plasma sodium and potassium concen tration and excretion thereof in urine, plasma osmolality, total prote in plasma concentration, whole blood haemoglobin and haematocrit conce ntration were measured. In the HKR group water and food intakes decrea sed significantly (p less than or equal to 0.05) when compared with th e VCR group, whilst diuresis, excretion of sodium and potassium in uri ne, plasma sodium and potassium concentration, plasma osmolality, plas ma protein concentration, whole blood haemoglobin and haematocrit incr eased significantly (p less than or equal to 0.05) when compared with the VCR group. It was concluded that prolonged exposure to HK induces significant changes in water balance and in both urinary and plasma so dium and potassium in rat.