Influence of Citric Acid Administration upon Renal Ammoniagenesis in the Acidotic Dog and Rat

Abstract

Citric acid reduced ammoniagenesis both in vitro and in vivo by the acidotic dog kidney. In the dog, renal cortical levels of citric acid, α-ketoglutaric acid (α-KG), glutamate, and glutamine were lower in the acidotic than nonacidotic state. Citric acid administration elevated tissue citric acid level 10-fold above the acidotic level, but levels of α-KG, glutamate, and glutamine remained unchanged. In kidney slices taken from acidotic dogs, citric acid levels were greatly elevated reducing ammonia production but failing to increase tissue glutamate. In the acidotic rat kidney, citric acid inhibited ammoniagenesis by incorporating ammonia into glutamate and glutamine. Although citric acid reduces ammoniagenesis in both acidotic rat and dog kidney, the rat kidney produces glutamine and glutamate while the dog kidney does not; consequently the mechanism by which citric acid influences ammoniagenesis appears to differ in the species.