Collagen metabolism in the retina of normal and diabetic rats

Glucosyltransferase, an enzyme involved in the synthesis of the carbohydrate portion of basement membranes and collagens, and collagen content were determined in the retina of normal and streptozotocin diabetic rats. No significant difference in glucosyltransferase activity was found at 4 weeks of diabetes. However, the enzyme activity was significantly increased in diabetic rats 12 and 48 weeks following the induction of diabetes. Similarly, a significant increase in collagen content was observed in diabetic retinas after 12 weeks of diabetes. Electron microscopy showed marked thickening of the retinal capillary basement membrane in long-term diabetic (48 weeks) rats. The data suggest that enhanced collagen synthesis and deposition occurs in the retina of diabetic rats, and with duration of diabetes this may result in thickening of the capillary basement membrane. These results are compatible with previously reported increases in kidney glucosyltransferase, collagen synthesis and thickening of the capillary basement membrane in diabetic rats.