Hepatic intralobular mapping of fructose metabolism in the rat liver

Detailed mapping of glucose and lactate metabolism along the radius of the hepatic lobule was performed in situ in rat livers perfused with 1.5 mM lac tate before and during the addition of 5 mM fructose. The majority of fruct ose uptake occurred in the periportal region; 45%, of fructose taken up in the periportal half of the lobular volume being converted into glucose. Per iportal lactate uptake was markedly decreased by addition of fructose. Basa l perivenous lactate output, which was derived from glucose synthesized per iportally, was increased in the presence of fructose. During fructose infus ion there was a small decrease in cell pH periportally, but acidification o f up to 0.5 pH units perivenously. The evidence suggests that ba situ the a pparent direct conversion of fructose into lactate represents, to a substan tial extent, the result of periportal conversion of fructose into glucose a nd the subsequent uptake and glycolysis to lactate in the perivenous zone o f some of that glucose. P-31 NMR spectroscopy showed that the cellular conc entration of phosphomonoesters changes very little periportally during fruc tose infusion, but there was an approximate twofold increase perivenously, presumably due to the accumulation of fructose 1-phosphate. it may be infer red that fructokinase activity is expressed throughout the hepatic lobule.