Effect of Extracellular Electrolyte Depletion on Water Intake in Dogs

Abstract

To determine whether or not cellular hydration is the mechanism regulating intake of fluids, the extracellular electrolytes were depleted in 11 expts. on 7 dogs by the interperit. dialysis technique. The animals were then maintained on a low salt diet for a period of 8-35 days. Immediately after electrolyte depletion all animals were profoundly depressed. This depression however gradually wore off and the dogs started to drink. In the animals which kept on eating while on the salt-poor diet, the fluid intake increased and remained above control levels for the duration of the salt depletion, while plasma chloride levels, plasma and thiocyanate fluid volumes remained low and body wt. was essentially unchanged. Urine excretion paralleled the fluid intake. In animals that refused the salt-poor food, the fluid intake was greater than that found when the same animals in normal electrolyte balances were deprived of food. On restoration of extracellular electrolytes, all measurements returned to control values. These findings are not in accord with the concept that the degree of cellular hydration determines the fluid intake.