Effect of acid and alkaline K phosphate on acid and electrolyte excretion in dogs

Abstract

Acidic or buffered potassium phosphates, given i.v. to dogs, induced increases of excretion of potassium, phosphate and of sodium. Maximal values of excretion were 865 µmoles/min/m2 for phosphate, 760 for potassium, 283 for titratable acid and 622 for sodium. Titratable acid increased after KH2PO4 and remained constant after K2HPO4-KH2PO4 (pH 7.4). Then, a technique of adding K+ without changing osmotic or phosphate load of infusion fluid was used. Acidic, buffered or dibasic potassium phosphates were substituted stoichiometrically for buffered sodium phosphate during periods of excretion of titratable acid at levels of 250–450 µmoles/min. After K+ substitution, excretion of sodium decreased before that of K+ changed. Then excretion of K+ increased while that of Na and phosphate remained fixed. Excretion of titratable acid increased in parallel with that of K+ after KH2PO4 and remained constant after K2HPO4. Excretion of titratable acid decreased while that of K+ increased after substitution of buffered potassium phosphate. Plasma CO2 content remained constant or increased after K+ substitution. Data could be explained on the basis of a tubular system of anion (H2PO4–) secretion, as well as on the basis of K+-H+ ion exchange for Na+ reabsorption.