Evidence That Choline Can Exchange for Hydrogen Across Proximal Tubules of Dogs

Abstract

Experiments were, carried out to test the hypothesis that choline can exchange for sodium ion across the proximal tubule and replace hydrogen for sodium ion exchange. Close arterial injection of choline chloride containing solutions indicates that choline enters luminal fluid by an extraglomerular path. Appearance of choline is accompanied by a decrease in U_Na+. In like experiments, hydrogen ion was also found to acidify urine by an extraglomerular path. Urinary acidification in these experiments was not accompanied by any meaningful change in sodium excretion. In model experiments, it was found that choline can compete effectively with hydrogen ions for exchange against sodium across a cation exchange membrane. Choline counteracts the natriuresis induced by Diamox. The results of these experiments are discussed and are considered to be consistent with the hypothesis tested.