Amiloride prevents the metabolic acidosis of a KCl load in nephrectomized rats

1. Counter movements of K⁺ and H⁺ across cell membranes were studied in nephrectomized KCl-loaded rats. In one group of animals, the movements of K⁺ and H⁺ were determined during and after a KCl load, and in another group, amiloride was used in order to evaluate Na⁺ participation in K⁺/H⁺ exchange.

2. After a KCl load at constant Pco₂, 79% of infused K⁺ left the inulin space, half of which was in exchange for H⁺. As a result, blood pH fell from 7.40 ± 0.01 to 7.30 ± 0.01 (mean ± sem; P < 0.001).

3. During KCl infusion, the K⁺/H⁺ exchange ratio varied between 1.3 and 6.8, showing that the coupling ratio is not fixed.

4. Amiloride did not change blood pH and plasma [K⁺], but prevented the metabolic acidosis produced by the KCl load without affecting K⁺ entry into the non-inulin space. Therefore, K⁺ and H⁺ movements became completely dissociated.

5. The results indicate that KCl activates an amiloride-sensitive H⁺ extrusion from the cells. This finding is compatible with the view that Na⁺/H⁺ exchange participates in the metabolic acidosis produced by a KCl load.