Erythrocyte glyceraldehyde-reductase levels in diabetics with retinopathy and cataract.

The activity levels of glyceraldehyde reductase, an aldose-reductase-like enzyme present in the erythrocyte, were determined in 104 subjects, who were divided into five groups--diabetics with retinopathy and cataract, diabetics with retinopathy and no cataract, diabetics with no retinopathy and no cataract, non-diabetics with senile cataract, and non-diabetic normal controls. Diabetics with retinopathy and cataract had significantly higher mean enzyme activity levels than normal control subjects (2.5 fold increase, p < 0.001); so had diabetics with retinopathy but no cataract (2 fold, p < 0.01) and patients with senile cataract (1.5 fold, p < 0.05). Juvenile diabetics had a significantly higher enzyme level than maturity onset diabetics. There was no significant difference in glyceraldehyde reductase between normal controls and diabetics without retinopathy or cataract, and no significant difference in polyol-dehydrogenase activity levels between any group studied. Enzyme activity did not correlate with age or glycosylated haemoglobin (HbA1c) levels. The increase in levels of erythrocyte glyceraldehyde reductase were due to increased amounts of active enzyme, rather than to elaboration of new kinetic pathways.