Untersuchungen an wachen Hunden über die Einstellung der Natriumbilanz

Summary

24 hour sodium and potassium balances, ECF (inulin space) and GFR (inulin clearance) were determined in trained dogs which had been maintained on high salt or low salt diets. Special attention was directed toward the transition period when animals were switched either from a low salt to a high salt intake, or vice versa.

1. When salt depleted dogs were switched to a salt intake of 1.7 or 14 mEq/kg and day, ECF increased to a maximum of 22±1.7% of body weight. This value was reached within 1–2 days when the higher salt intake was used, and within 8–9 days when the lower amount was added to the food.

2. When, in these same dogs, salt feeding was stopped and food with about 0,5 mEq/kg and day (sodium poor diet) was given, the ECF remained unaltered for about 2 weeks. After this period it decreased continously, reaching a new steady state value of 16% of body weight within 4 months.

3. GFR, measured at 8 a.m. and before feeding, did not change despite these variations in ECF.

4. With high sodium diet (14 mEq/kg and day) a negative potassium balance appeared. This was greatest on the first day. During a 5 day period the potassium loss was 5 times greater than the extracellular potassium store, indicating an intracellular depletion.

5. These results may imply an important role for body fluid volumes in the regulation of salt balance.