ELECTROLYTE CONCENTRATION IN SKELETAL-MUSCLES AND PLASMA OF RATS DURING AND AFTER EXPOSURE TO HYPOKINESIA AND HYPERHYDRATION

The objective of this investigation was to determine electrolyte conce ntration in skeletal muscles and plasma of rats during 90 days of hypo kinesia (decreased motor activity) and 15 days of posthypokinesia, The animals were divided into three groups: 1) supplemented hypokinetic r ats (SHR), i.e., rats subjected to hypokinesia and taking daily an add itional 9 mi water per 100 g body weight plus 6 mi isotonic sodium chl oride per 100 g body weight; 2) unsupplemented hypokinetic rats (UHR), i.e., rats subjected to hypokinesia; 3) vivarium control rats (VCR), i.e., rats placed under ordinary vivarium conditions. Hypokinesia was effected by keeping SHR and UHR animals in small individual cages that restricted their movements in all directions without hindering food a nd water intake. Determinations were made of water and electrolyte (so dium, potassium, calcium, magnesium) concentrations in muscle tissue; concentration of electrolytes (sodium, potassium, calcium, magnesium, phosphorus, chloride) in plasma; body weight; fluid consumed and elimi nated in urine; whole blood, red blood cell and plasma volumes; hemato crit content and plasma protein concentration. During the hypokinetic period, electrolytes and water concentration in muscle tissue and plas ma electrolyte concentration changed significantly in the UHR when com pared with SHR and VCR while in comparing the SHR with the VCR these s ame variables had no significant changes. Body weight, water balance, volume of blood, red blood cell and plasma, hematocrit and plasma prot ein concentration in the UHR were also significantly different when co mpared with the VCR. No significant difference was seen in these param eters when the SHR and VCR were compared. During the initial seven day s of the posthypokinetic period the changes in these same parameters r emained significantly different in the UHR when compared with the SHR and VCR while changes were insignificant when the SHR and the VCR were compared, It was concluded that daily hyperhydration may be used to a ttenuate or normalize water and electrolyte concentrations in muscles and plasma of rats subjected to prolonged restriction of motor activit y.