Diabetes, Vol 42, Issue 6 820-825, Copyright © 1993 by American Diabetes Association
Aldose reductase inhibition fails to prevent retinopathy in diabetic and galactosemic dogs
RL Engerman and TS Kern
Department of Ophthalmology, University of Wisconsin-Madison.
To investigate a possible role of excessive polyol production in the
pathogenesis of diabetic retinopathy, 16 ALX-induced diabetic dogs and 20
experimentally galactosemic dogs were randomly assigned to 5 yr of
treatment with either sorbinil, an aldose reductase inhibitor, or a
placebo. The severity of hyperglycemia in sorbinil-treated and placebo
groups was monitored throughout the 5-yr study by assay of glycosuria and
nonenzymatically glycated plasma protein and HbA1 needed in an effort to
avoid confounding possible group differences in hyperglycemia severity with
possible drug effects. Inhibition of polyol production by sorbinil was
monitored in erythrocytes throughout the study and also in retina and other
tissue obtained at autopsy. Trypsin digests of retinal vessels were
compared after 60 mo of diabetes and after 42 and 60 mo of galactosemia. In
diabetic dogs, development of retinopathy was not significantly influenced
by a sorbinil dose (20 mg.kg-1 x day-1) sufficient to prevent elevation of
sorbitol levels in retina and other tissue. Likewise, in dogs made
experimentally galactosemic for 42-60 mo, administration of sorbinil (60-80
mg.kg-1 x day-1) had no significant effect on the development of
retinopathy notwithstanding prevention of 93-96% of the polyol elevation in
retina and other tissue. Retinal capillary basement membrane was
significantly thicker than normal in diabetic and in galactosemic dogs and
was not significantly influenced by administration of sorbinil in either
dog model. Thus, no evidence was found that the development of retinopathy
is critically dependent on excessive polyol production or accumulation.