Identification of fructose as the retinopathic agent associated with the ingestion of sucrose-rich diets in the rat.

In order to determine whether the fructose moiety of sucrose or the lack of some factor essential for the integrity of the microvascular system was responsible for the development of sucrose retinopathy in the rat, a series of diets containing possible sources of such a factor and/or fructose was tested over a 6-mo period. Examination of the isolated rat retinal vascular systems showed conclusively that fructose was the dietary microangiopathic agent associated with sucrose-induced retinopathy. The microvascular lesions produced were similar to those found in diabetic rats maintained over the same period. Cross-sectional studies of the retinas revealed that microvascular lesions preceded the associated degeneration of neural tissue rather than vice versa since the majority of rats with retinopathy showed no signs of neural damage. Sucrose feeding was found to produce a significant elevation (p < 0.001) in blood fructose concentration and a slight increase, albeit not significant (p < 0.01), in retinal fructose-1-phosphate (F1P) levels. The results are discussed in relation to the changes in retinal sorbitol, fructose, FIP, and lactate metabolism found in diabetes.