SODIUM, POTASSIUM AND WATER METABOLISM IN THE RABBIT - EFFECT OF SODIUM DEPLETION AND REPLETION

Dietary Na depletion and subsequent repletion was studied in rabbits. K intake was maintained constant. During Na depletion and repletion blood pressure, packed cell volume, food consumption and body weight remained at control values. Decreased Na excretion was observed in urine and feces during Na depletion and the physiological control of these changes is discussed in relation to the renin-angiotensin-aldosterone system. K excretion during Na depletion initially fell as a result of reduced urine volume and gradually returned to normal. Urine K concentration remained constant. Fecal excretion of K rose by 63% during Na depletion and there was a rise from a control value of 17-25% in the proportion of total K excretion accounted for by the fecal component. Water consumption and urine volume decreased in the initial phase of Na depletion and then returned to control levels. It is important to consider urinary and fecal excretion of Na and K when calculating balance status for either ion. Fecal excretion and kidney function both show important physiological adaptations.