Renal gluconeogenesis in man: comparison with rats and rabbits

To provide evidence on renal gluconeogenesis in humans and to compare with rats and rabbits, glucose production from several substrates was determined using cortical slices of the three species. In humans, the normal parts of kidney tissue were obtained from six cases of transitional cell carcinoma of the renal pelvis and four cases of renal cell carcinoma. Renal cortical slices were incubated aerobically with or without substrates, and the glucose contents were assayed photometrically. The specificity of human kidneys was evaluated by comparison with the results obtained from rats and rabbits. The rank order of renal gluconeogenesis from various substrates was as follows: Humans: pyruvate > oxaloacetic acid > lactic acid > fructose-1,6-diphosphate > L-glutamine. Rats: pyruvate > fructose-1,6-diphosphate > oxaloacetic acid > lactic acid > L-glutamine. Rabbits: fructose-1,6-diphosphate > pyruvate > oxaloacetic acid > lactic acid >> L-glutamine = 0. In general, the human kidney can produce glucose at the lowest rate among the three species. The substrate specificity of humans was more or less similar to that of rats. These results suggest the existence of a species difference in renal gluconeogenesis both in substrate specificities and quantitative activities.