Pathways of Glucose Metabolism in the Lens.

In the lens the biological energy necessary for the maintenance of transparency, synthesis, and repair is supplied primarily by the reactions that metabolize glucose to lactic acid. The low levels of the enzymes associated with the aerobic oxidation of glucose restrict the lens metabolism mainly to anaerobic glycolysis. Even in the epithelium, anaerobic glycolysis appears Jo be the principal source of biological energy. The evidence for this is that the active transport mechanisms of the lens occur primarily in the epithelium and these energyutilizing processes can be almost entirely supported by anaerobic glycolysis. Another unusual feature of lens glucose metabolism is the ability of the lens to' synthesize sorbitol. It is the unusual set of circumstances of low hexokinase, relatively high aldose reductase, and high pentose shunt activities which render the lens a favorable site for sorbitol production.