Carbohydrate metabolism in rat kidney: heterogeneous distribution of glycolytic and gluconeogenic key enzymes.

The distribution pattern of the unidirectional enzymes of gluconeogenesis and glycolysis, fructose-1,6-bisphosphatase (EC 3.1.3.11) and phosphofructokinase (EC 2.7.1.11), within the nephron was studied by the microdissection and oil-well techniques according to LOWRY and PASSONNEAU [11]. Fructose-1,6-bisphosphatase activity was found to be highest in the proximal convolution, whereas phosphofructokinase revealed its highest activity in the thick ascending limb of Henle's loop. Starvation and NH4Cl acidosis led to an increase of fructose-1,6-bisphosphatase activity in the proximal convolution. These results indicate a clear separation of the glucose synthesizing and degrading pathways within the nephron, which is maintained in conditions that stimulate gluconeogenesis.