Chronic potassium loading in dogs. Effect of sodium intake on acid-base equilibrium

Chronic oral potassium (K) loading with subsequent alteration in sodium (Na) intake was accomplished in 12 normal dogs in order to investigate the influence of Na intake on acid-base equilibrium in the chronically K-loaded animal. Chronic K loading (20 mEq/kg/ day) for 7-21 days did not result in alteration in acid-base status as compared to control when adequate Na (2.5 mEq/kg/day) was ingested. Mild steady state metabolic acidosis occurred during Na restriction (10.1 ± 0.3 mEq/liter vs. 21.6 ± 0.3 mEq/liter HCO₃, p < 0.001) associated with decreased K excretion (-18 ± 6 mEq/day, p < 0.01) and modest elevation of plasma K (4.4 ± 0.1 vs. 3.9 ± 0.1 mEq/liter, p < 0.01). Metabolic balance studies which were performed in 6 of the animals failed to reveal significant changes in net acid excretion to account for either the persistent acidosis occurring during Na restriction or the correction which occurred with return of dietary Na. These findings demonstrate that acid-base homeostasis may be maintained despite massive chronic K loading in the dog and suggest that this ability may be limited when Na intake is rigidly restricted.