CORRELATION BETWEEN RATES AND ENZYME LEVELS OF INCREASED GLUCONEOGENESIS IN RAT-LIVER AND KIDNEY AFTER PARTIAL-HEPATECTOMY

The metabolic rates and key enzymes of gluconeogenesis and glycolysis were determined and correlated in perfused livers, isolated hepatocyte suspensions and kidney cortex slices of rats after two‐thirds hepatectomy. Fed unoperated, sham operated and fasted animals served as controls. In liver the following results were obtained. Firstly, after partial hepatectomy [14C]glucose formation from [14C]lactate was increased in perfused livers to 223% after 24 h and to 173% after 48 h and in hepatocyte suspensions to 222% after 48 h. [14C]Glucose production from [14C]fructose, however, was unchanged. These metabolic rates correlated well with an increase of the level of phosphoenolpyruvate carboxykinase to 206% after 24 h and to 184% after 48 h. The levels of fructose‐1,6‐bisphosphatase and glucose‐6‐phosphatase were unaltered. Secondly, after a 24‐h fast gluconeogenesis from lactate was enhanced to 282% in perfused livers and to 300% in hepatocyte suspensions. Gluconeogenesis from fructose was slightly increased to 140%. These altered rates were accompanied by an increase of phosphoenolpyruvate carboxykinase to 213% and of glucose‐6‐phosphatase to 190%. Thirdly, after partial hepatectomy [14C]lactate formation from [14C]glucose was decreased in hepatocyte suspensions to less than 20% after 48 h. [14C]Lactate production from [14C]fructose was unchanged. These rates coincided with a decrease of the level of glucokinase to 40% and with unaltered levels of phosphofructokinase and pyruvate kinase. Fourthly, after a 24‐h fast glycolysis from glucose was lowered to below 30%. This rate was paralleled by a decrease of the level of glucokinase to 60%. In kidney cortex the following results were obtained. Firstly, after partial hepatectomy gluconeogenesis from lactate was enhanced in tissue slices to 217% after 24 h. Gluconeogenesis from fructose was unchanged. These rates coincided with an increase of the level of phosphoenolpyruvate carboxykinase to 193% and of glucose‐6‐phosphatase to 151%. Secondly, after a 24‐h fast similar changes for the gluconeogenic rate to 200% and of phosphoenolpyruvate carboxykinase to 240% as well as of glucose‐6‐phosphatase to 136% were observed. Thirdly, neither the rates of glycolysis nor the levels of hexokinase, phosphofructokinase and pyruvate kinase were altered after partial hepatectomy or a 24‐h fast. No significant changes neither in liver nor in kidney cortex occurred after sham operation. Thus the drastic reduction of liver tissue after partial hepatectomy was compensated by an increase of gluconeogenesis in the liver remnant and in kidney cortex, both accompanied by an enhancement of the phosphoenolpyruvate carboxykinase level, in order to maintain the glucose homeostasis. Copyright © 1979, Wiley Blackwell. All rights reserved