Glycolysis and its interaction with a gluconeogenic precursor in perfused rat liver.

A non-recirculating, haemoglobin-free perfusion system was used to evaluate glycolysis in livers from fasted rats. Glycolysis was calculated from lactate and pyruvate production before and after infusion of glucose. In the absence of extracellular glucose glycolysis was small. Stimulation of glycolytic flux occured at extracellular glucose concentrations above 5 mM. Rates were proportional to glucose concentrations. Glycolysis was also investigated in the presence of extracellular lactate, which is a precursor of gluconeogenesis. High glucose concentrations (15-35 mM) were followed by lactate and pyruvate output suggesting that glycolysis was prevailing. Estimated flux rates, however, were significantly lower in the presence of the gluconeogenic precursor. Our results provide arguments that gluconeogenesis and glycolysis interact in order to regulate the peripheral glucose concentration.