Excretion of Krebs cycle acids in relation to the cycle's function in avian kidney

¹ Department of Physiology, University of Rochester School of Medicine and Dentistry, Rochester, New York

In the chicken, unilateral renal portal perfusion with certain intermediates of the Krebs cycle (notably sodium -ketoglutarate, succinate, and fumarate) increased excretion of other cycle acids, particularly citrate and -ketoglutarate. These were excreted at a much higher rate from the ipsilateral kidney. This phenomenon was even more striking during infusion of sodium pyruvate with one-seventh the amount of sodium fumarate, -ketoglutarate, or oxaloacetate. This resembles the catalytic, or "sparking" effect of these same dicarboxylic acids on pyruvate oxidation by the Krebs cycle in certain tissues, a resemblance strengthened by the fact that this sparked excretion of cycle acids is blocked by sodium malonate or ammonium salts which also block the effect in tissues. These observations are discussed in terms of 1) the possible renal tubular synthesis and secretion of these cycle acids from their infused precursors, and 2) the increased excretion of citrate and -ketoglutarate in alkalosis.

Key Words: organic acid excretory mechanism • tricarboxylic acid cycle • renal tubular synthesis and secretion • pyruvate oxidation • oxidative energy metabolism • catalytic effect of intermediary dicarboxylic acids • alkalosis

Submitted on May 23, 1963