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Abstract
The transport of glucose into the lens is reviewed against a background of data on glucose transport in muscle and the red blood cell. In muscle, sorbitol does not penetrate the cell membrane and is limited to the extracellular space. On the other hand, 3-0-methylglucose is distributed in most of the tissue water. Similar results are obtained in lens. The glucose that is found in muscle and lens can be accounted for on the basis of the glucose that would be expected to be in the extracellular space. Thus, transport is a limiting step in glucose metabolism and the rate of utilization of glucose may be equated with the rate of inward transport. Mediated transport is considered as taking place at the fiber membrane. The kinetics of glucose transport in the lens are similar to those in muscle and the red blood cell. All three have Km values of about 7.0 mM. and Q10 values of 2.0. Glucose competes with 3-0-methylglucose for the transport system in the lens. Glucose transport in the lens, as it is in muscle, is enhanced by respiratory poisons and inhibited by glycolytic poisons and phlorizin. It is concluded that the process of glucose transport in the lens is similar to that in tissues such as muscle and the red blood cell.