Glucose Metabolism and Fructose Synthesis in the Diabetic Rat Lens

¹ Kresge Eye Institute, Detroit, Mich.

A comparison of the uptake of glucose in vitro by lenses from normal and alloxan-diabetic rats involves the effect of secondary factors tuhich may obscure any effect of diabetes itself. These factors have been investigated and their influence evaluated. A procedure has been developed for the incubation of lens dispersions which yields values for glucose uptake and. lactate production within the normal range for intact lenses in Tyrode's solution. The results of this investigation show that the rate of uptake of glucose by dispersions of diabetic lenses is about 80 per cent of normal. Furthermore, it is shown that the amount of fructose produced, by dispersions of diabetic lens is equivalent to 20 per cent of the glucose taken up, a fraction five times that for normal lens dispersions. Making the likely assumption that the depletion of the sorbitol pool in diabetic lenses is no greater than it is in normal lenses, the diabetic lenses would actually have available for energy production only about 80 per cent of the glucose taken up. On the basis of this reasoning the diabetic lenses obtain energy from the metabolism of glucose at a rate only 60 per cent of normal. It is possible that diabetic cataracts may in part be the result of decreased production of energy. The conversion of sorbitol to fructose leads to a diversion of DPN which quantitatively is equivalent to the 20 per cent depression of glucose uptake found in diabetic lenses. It is suggested that this depression of glucose uptake maybe a result of the diversion of DPN from anaerobic glycolysis.