Renal excretion of potassium in the sheep

1. Observations were made on the daily intake and excretion of potassium and sodium in sheep housed in metabolism cages and fed once daily. 2. The diet of chaffed hay and crushed oats provided 400‐600 m‐moles K and 50‐60 m‐moles Na daily. About 90% of the K was excreted in the urine, and over 90% of the Na was found in the faeces. 3. In two groups of three experiments on each of three sheep, the urinary responses to intra‐ruminal dosing just before feeding of (i) 1 l. distilled water, (ii) 1 l. 0·25 N ‐KCl, and (iii) 1 l. 0·125 N ‐NaCl, were studied. In the first group, urine was collected via the urine/faeces separator of the metabolism cage, whereas for part of the experiments in the second group it was collected by an indwelling bladder catheter. 4. In a third group of experiments with the same sheep, the effects on urinary excretion of K and Na of intra‐ruminal dosing with (i) 1 l. distilled water, (ii) 1 l. 0·25 N ‐K acetate, and (iii) 1 l. 0·25 N ‐Na acetate were investigated. During part of these experiments urine was again collected via an indwelling bladder catheter. With chloride, 82% of the additional potassium was excreted in urine in the 24 hr after dosing, but with acetate only 65%. For sodium, the corresponding figures were 12‐40% with chloride and 43% with acetate. 5. In most experiments, the administration of K salts produced a marked kaliuresis and, in spite of the low sodium intake, a natriuresis as well, which did not usually coincide with maximum K excretion. No adequately tested explanation appears to exist for the natriuresis observed in response to treatment with K salts.