ALTERATIONS IN BODY COMPOSITION WITH SODIUM LOADING AND POTASSIUM RESTRICTION IN THE RAT: THE TOTAL BODY SODIUM, NITROGEN, MAGNESIUM AND CALCIUM 1

Abstract

Changes in body composition with respect to electrolytes, N and water were studied in rats given diets low in K and either isotonic NaCl or sodium bicarbonate for drinking. Desoxycorticosterone acetate (DCA) was administered to some of the groups. In comparison with normal animals, K restricted animals showed an increase in total body Na, a reduction in K and, in those groups in which the animals remained in good nutritional status, a fall in body chloride. The changes appeared dependent on K restriction in that animals given saline for drinking and a normal diet had no change in body composition. Animals subjected to conditions so rigorous that significant weight loss occured had an increase in body chloride per unit of fat free dry solid but the chloride content of the whole carcass, judged on the basis of the content at the outset of the experiment, showed little change. Starvation appears to markedly affect the relationship of body electrolyte to fat free dry solid. The carcass content of Ca, Mg and N per unit of fat free dry solidwas not affected by K restriction. Animals receiving DCA in addition to K restriction had a much greater retention of Na in the chloride space and a more marked alkalosis than animals subjected only to K restriction. The extent of K depletion could not be correlated with the gain in body Na, with changes in acid base balance or with the serum level of K.