Characteristics of potassium conservation by the dog kidney

During simultaneous restriction of sodium and potassium to 1 and 2 mEq/day, respectively, it has been demonstrated that the dog kidney has a remarkable capacity to conserve potassium, the urinary excretion of this ion decreasing rapidly to equal the intake within 4–5 days. Subsequent administration of sodium 100 mEq/day in the form of chloride failed to influence renal conservation of potassium. Equivalent administration of sodium in the form of sulfate or neutral phosphate resulted in a transient but unequivocal increase in urinary excretion of potassium. When desoxycorticosterone 1 mg/kg day was given while high sodium intake and potassium restriction was continued, significant increase in urinary excretion of potassium was observed regardless of the anionic form in which sodium was given. It is suggested that chloride, a readily permeant anion, may prevent significant tubular sodium-potassium exchange. This effect would appear to be overcome when large amount of mineralocorticoid is acting on the renal tubules.