The effects of xylose on the isolated lens.

The effects of D-xylose on the rat lens were studied using lens culture techniques. At 30 mM xylose a dramatic increase in lens water was accompanied by opacification of the lens. The osmotic change was apparently caused by the accumulation of xylitol and an increase in total electrolytes. All these changes were prevented from occurring when 1 mM of AY-22,284, an aldose reductase inhibitor, was included in the xylose-containing medium. Of the three cataractogenic sugars the order of effectiveness in producing changes in lens water and polyol levels was D-xylose, D-galactose, and D-glucose. This observation was consistent with the substrate specificity properties of lens aldose reductase. Of these sugars, the most active substrate is D-xylose; D-galactose is next, and D-glucose is the least active for this enzyme. In lens culture the aldose reductase inhibitor can suppress the deleterious effects of these sugars. All these facts suggest that the action of aldose reductase is probably the initiating factor in sugar cataract development.