Gluconeogenesis and ammonia production in the isolated perfused rat kidney: the effect of starvation, acidosis and diabetic ketosis.

Isolated rat kidneys were perfused with a cell-free perfusate, and their creatinine clearance was found to be 106 I'll min.1 g wet weight. Gluconeogenesis from pyruvate, lactate, fructose, a-oxoglutarate, oxaloacetate, glutamate and glutamine as the substrates at a concentration of 10 mM and ammonia production from glutamine were studied in the kidneys from fasted rats, rats with NH.CI-induced acidosis, and streptozotocin diabetic rats, using cell-free perfusates. I. Fasting caused the gluconeogenesis from all substrates except pyruvate and the ammonia production from glutamine to increase. 2. In the kidneys from the rats with chronic acidosis, the gluconeogenesis from the substrates other than pyruvate, lactate and fructose was increased, and the gluconeogenesis and ammonia production from glutamine were both greater than those in the kidneys from the 7-day fasted rats. 3. In the kidneys from the streptozotocin diabetic rats, the gluconeogenesis from all substrates other than fructose was increased and was greater than that in the kidneys from the fasted rats and the rats with chronic acidosis. Also, despite the markedly increased gluconeogenesis from glutamine, ammonia production did not increase. From these findings, we believe that gluconeogenesis and ammonia production are not always coupled with each other, especially under some conditions in tho isolated perfused rat kidneys.