The effect of sodium depletion of the renal response to water-loading in dogs.

1. Dogs depleted of sodium by peritoneal dialysis with glucose solution (5 g/100 ml.) showed a significant reduction in plasma sodium concentration, in inulin clearance and in plasma and extracellular fluid volume. The plasma protein concentration and haematocrit were increased.2. By the second day of salt depletion the plasma and extracellular fluid volumes, plasma protein concentration and haematocrit all showed some recovery towards normal values.3. A water-load of 2.5% of body weight did not cause diuresis or natriuresis when given on the first day of depletion, but initiated a water diuresis when given on the second day.4. A water-load of 5% of body weight caused diuresis but not natriuresis, when given on either day of salt depletion.5. The physiological interpretation of these results is discussed.