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Abstract
Evidence has been presented supporting the concept of a mediated transfer of certain sugars into calf and rat lenses. This conclusion was reached from observation of structural requirements for entry of closely related sugars into calf lens, and from a kinetic analysis of the entry of sugars into the rat lens. At high sugar concentrations, saturation of the binding sites and competition between pairs of monosaccharides were demonstrable in the rat lens. Galactose appeared to have the potentiality of penetrating the cells of the rat lens by simple diffusion or by utilizing the binding sites. Glucose and fructose competed for utilization by calf lens with the former appearing to have five to six times the affinity of the latter. A number of carbohydrates apparently pass through the lens capsule but are unable to cross cellular membranes.