Metabolic Pathways in Experimental Diabetic Cataract

¹ Department of Surgery, Division of Ophthalmology, and the Department of Biochemistry of the University of Rochester School of Medicine and Dentistry, Rochester, N. Y.

Specific areas in carbohydrate and protein metabolism were studied in the lenses of alloxandiabetic rats. The studies were performed at weekly intervals commencing with the first week after diabetes had been induced and continuing until the fourth to fifth week. The results of these investigations indicate that lenticular anaerobic glycohjsis as reflected by lactate production and the recovery of C-14-O₂ from lenses incubated with glucose-6-C-14, remains relatively unchanged during the 4 to 5 week period compared with that from control animals. The concentration of glucose and fructose in the diabetic lenses shows a fifteen- to twentyfold increase one week after diabetes has been induced and remains at this elevated level throughout the experimental period. The recovery of C-14-O₂ from lenses incubated with glucose-l-C-14 shows a marked decline at the first week (in contrast with the recovery of C-14-O₂ from glucose-6-C-14) and remains low in the diabetic lenses throughout the 4 to 5 week period of observation. The level of ATP in the lenses also exhibits a similar decrease of approximately 35 to 40 per cent.

In studying the incorporation of C-14-labeled leucine, lysine, and valine, a marked decline in the degree of incorporation of these amino acids into lenticular protein quickly becomes manifest in the diabetic lenses. There is a similar decrease in the free amino acid concentration in the lenses which becomes apparent within the first week of diabetes.