MAINTENANCE OF POTASSIUM EXCRETION DESPITE REDUCTION OF GLOMERULAR FILTRATION DURING SODIUM DIURESIS

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Abstract
The excretion of potassium was studied in the dog during reduction of the glomerular filtration rate (GFR) by means of an inflatable cuff placed around one renal artery. In experiments in which no attempt was made to maintain high rates of Na excretion, K excretion fell with the decrease in the GFR. When high rates of Na excretion were maintained by administration of mercurials, sodium sulfate, or acetazolamide, the rate of K excretion was maintained in spite of reductions of the GFR by up to 40%. This was true both at low and high rates of K excretion. The results support the interpretation that reabsorption of filtered K is essentially complete, and that the urinary K is derived from secreted K. The dependence of K excretion on Na excretion provides evidence that the secretion of K occurs by an exchange of K for Na in the distal tubule.

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