AN ANALYSIS OF THE MECHANISM OF THE INHIBITORY INFLUENCE OF K+ ON RENAL H+ SECRETION*

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Abstract
The effect of K+ on the relationship of the HCO3- Tm to plasma PCO2 was studied in dogs before and after inhibition of carbonic anhydrase. It was found that K+ depressed HCO3- reabsorption to an equal extent before and after administration of acetazolamide, indicating that the depressant effect of K+ on HCO3- reabsorption was mediated entirely through a pCO2 dependent-carbonic anhydrase independent system. The mechanism of the inhibitory effect of K+ was examined by means of Michaelis-Menten kinetics. From the fact that the inhibitory effects of K+ were greatest at high pCO2 tensions and that the Vmax, but not the Km, was lowered, it was suggested that the action of K+ may be mediated by a process of noncompetitive inhibition or by a competitive process in which intra-cellular alkalinization plays a significant role.

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