Reabsorption and secretion of -malic acid in kidney proximal tubule

¹ Department of Pharmacology, Queen's University, Kingston, Ontario, Canada

The -malic excretion pattern was studied in the dog using the "stop flow" method. During -malic and fumaric infusions, a net reabsorption of -malic acid was seen only in the proximal tubule. This reabsorption occurred against a massive concentration gradient and, therefore, was justifiably termed active reabsorption. Infusion of succinate produced a net secretion of -malic. This was also confined to the proximal tubule. The secretion, however, occurred in the direction of the concentration gradient and, therefore, was probably a diffusion phenomenon. The secretion could be inhibited by malonate. It was concluded that the renal transports of -malic acid are intimately related to the operation of the tricarboxylic acid cycle.