Glucose oxidation in the chick cornea: effect of diamide on the pentose shunt.

radiolabeled carbon 1 ( 14 C-1) of glucose to radiolabeled carbon 6 ( 14 C-6) of glucose derived as expired i4 CO2- Diamide and NEM were both found to increase pentose shunt activity relative to glycolysis, although by different means. Diamide appeared to exert its effect by oxidizing glutathione and creating a demand for higher shunt activity to facilitate glutathione reduction by NADPH. Both C-l and C-6 oxidation were increased, but C-l oxidation was increased to a much greater extent. In contrast, NEM decreased both C-l and C-6 oxidation, with C-6 preferentially affected. Thus NEM appears to preferentially inhibit the enzymatic machinery of the glycolytic-tricarboxylic acid cycle pathway and acts as an effective metabolic stress on the cornea. Our data suggest that the pentose shunt in the cornea may serve as an important alternative pathway under conditions of metabolic stress for glucose utilization and the production of energy (ATP) in the corneal cells.