The distribution of aldose reductase and aldehyde reductase II in different regions of bovine lens

The distribution of aldose reductase and aldehyde reductase II in the epithelium, cortex and nuclear regions of the bovine lens has been studied. The levels of the two enzymes in different regions of the bovine lens were determined after partial purification by DEAE-cellulose (DE-52) column chromatography. Aldose reductase was present in all the three regions of the lens, whereas aldehyde reductase II was present mainly in the epithelium and cortex. The activity of the enzymes, expressed per mg protein, was 10-15 fold higher in lens epithelium as compared to cortex and when expressed per g tissue wet weight, was approximately 2 fold higher. Substrate specificity of aldose reductase purified from all three regions of the lens was comparable, but the susceptibility to inhibition by various aldose reductase inhibitors was significantly different. As compared to the enzyme of cortex and nucleus, the epithelial aldose reductase was less (30-40%) susceptible to inhibition by aldose reductase inhibitors such as sorbinil, tolrestat, statil and tetramethylene glutaric acid. The substrate specificity and characteristics of inhibition of aldehyde reductase II purified from epithelium and cortex were similar.