Age-related changes in the water and electrolyte metabolism in male rats of the Wistar/TW strain.

The changes of water intake, urinary volume, ratio of the water intake to the urinary output (water turnover rate) and urinary concentrations of sodium, potassium and chloride ions were investigated in male rats of the inbred Wistar/Tw strain during aging. Marked increase of the water intake, the urinary output and the water turnover rate as well as marked decrease of the urinary electrolyte concentrations were observed at the age of over 16 months. First signs of increase in the water intake and the water turnover rate were observed at the age of 12-13 months, but the initial reduction of urinary electrolyte concentrations was detected as early as at 7-9 months of age.