Renal excretion of choline in the dog

¹ Department of Physiology, University of Michigan, Ann Arbor, Michigan

Experiments on dogs, with clearance and stop flow techniques, demonstrated that choline is reabsorbed and secreted by the proximal tubule, both processes being active. These processes seem to occur simultaneously, net reabsorption predominating at normal plasma choline concentrations and net secretion often becoming manifest when plasma choline was elevated. Secretion could be inhibited by either cyanine dye no. 863 or a hemicholinium. Transport rates were extremely variable in different animals and constant in a single animal only for several hours. The distal nephron was found to be impermeable to choline. The degree of proximal permeability could not be quantitated. Passive transport did not appear to be significantly involved in choline excretion.