Enzymatic and metabolic studies on carbohydrate and amino acid metabolism in rat liver during acute uraemia.

Abstract

Abstract. Enzyme activities of the glycolytic, gluconeogenic, and hexose monophosphate pathways were measured in the liver of starved rats 12 and 48 hours after bilateral nephrectomy. Control experiments (sham operated rats) revealed that alterations of enzyme activities were not due to uraemia but to starvation. Alanine‐aminotransferase and aspartate‐ aminotransferase activities, however, were significantly elevated in rat liver 48 hours after nephrectomy when compared with sham operated controls. Concentrations of some of the gluconeogenic intermediates (3‐phosphoglyceric acid, pyruvate, phosphoenolpyruvate and glucose‐6‐phosphate) were significantly higher in the liver of uraemic animals. Amino acid analysis showed an increase in only L‐alanine concentration. It is suggested that the elevated content of pyruvate in the liver during acute uraemia is due to an inhibition of pyruvate degradation. Together with the elevated pyruvate concentration the increase in L‐alanine could be explained as a consequence of the equilibrium of the alanine‐aminotransferase reaction; Kapp. of the reaction is not changed by uraemia. Increased activities of the transaminases and the elevated concentrations of the other metabolites measured might indicate that in the liver of nephrectomized rats there is enhanced gluconeogenesis from substrates other than pyruvate.