Potassium reabsorption and secretion in the perfused bullfrog kidney

Techniques have been developed for obtaining comparative estimates of the rates of K secretion and reabsorption in the artificially perfused bullfrog kidney and the use of 42K infused into the portal circulation. In control experiments in which Kexc/Kfilt averaged 0.65, approximately 30% of filtered K escaped reabsorption and excreted K was composed of roughly equal parts of filtered K and secreted K. Fractional reabsorption of K was constant at 70% over a wide range of filtration rates. The rate of K secretion correlated significantly with the rate of Na reabsorption and with the urine flow rate. Acetazolamide stimulated secretion and inhibited reabsorption.