The polyol pathway in retinal microangiopathy.

Two structurally unrelated aldose reductase inhibitors (sorbinil and tolrestat) were used for assessing the possible role of aldose reductase in the thickening of retinal capillary basement membranes of rats. Rats were fed either a normal diet, a 50% galactose diet, or a 50% galactose diet with the addition of an aldose reductase inhibitor. Micrographs of capillaries in the outer plexiform layer of the retina were analysed. This showed that the basement membrane thickening and the ultrastructural changes in the retinal capillaries that were induced by the galactose diet were inhibited by the addition of an aldose reductase inhibitor. Thickening of the basement membrane may be related to other tissue lesions in diabetic retinopathy. Therefore, its prevention might have a favourable influence on other aspects of this retinopathy.