Real importance of alanine in renal metabolism: in vitro studies in rat and dog.

In vitro studies were performed on cortical renal tubules to clarify possible differences between dog and rat with regard to alanine production and to define more precisely the role of alanine on ammonia and glucose production by the kidney. It was established that glutamate-pyruvate transaminase has an activity that is seven times lower in the rat than in the dog kidney. At the same time, alanine production from lactate, pyruvate, and glutamate is three times lower in the rat than in the dog kidney. The enzymatic reaction could be completely inhibited in a competitive fashion with aminooxyacetate. O2 consumption and CO2 production by the renal tubules were lower than that observed with glutamine. CO2 production in the rat was lowest. Production of ammonia and glucose by the kidney from alanine during acidosis averaged less than 20% of that produced with L-glutamine. Furthermore, during metabolic acidosis the production of ammonia and glucose from alanine was not augmented and failed to be influenced by increasing the concentration of alanine in the incubation medium.