Tissue distribution of mammalian aldose reductase and related enzymes.
Activities of aldose reductase (AR) and related NADPH-dependent enzymes were examined in extracts of human, cat, dog, guinea pig, mouse, monkey, pig, rabbit, rat and sheep lenses and a variety of other tissues. The activity of the tissues against DL-glyceraldehyde, D-glucuronic acid, and 3-pyridinecarboxaldehyde (PCA) was determined. High glyceraldehyde:glucuronic acid activity ratios, a characteristic of aldose reductase, were found in all lenses, except from mouse. An analytical thin-layer isoelectric focusing system which separates the mammalian NADPH-dependent enzymes was developed. AR appears to be present as two or more isozymes in all mammalian lenses studied with the exception of mouse. Other tissues contain one or more isozymes which have the same isoelectric point and substrate specificity as the AR present in the lens of that species. This AR activity, however, may represent only a small proportion of the total NADPH reducing activity present. AR and HDH isozymes reduce the aromatic substrate, PCA, and thus have the general characteristics of an aldehyde reductase.