ALDOSE AND ALDEHYDE REDUCTASES FROM HUMAN KIDNEY CORTEX AND MEDULLA

Aldose reductase and aldehyde reductase were purified to homogeneity f rom multiple samples of human kidney cortex and medulla. A single form of aldose reductase is expressed in kidney that is kinetically and im munochemically indistinguishable from aldose reductase expressed in ot her human tissues. The results support the conclusion that there is a single human aldose reductase, and that aldose reductase is expressed in a reduced form, characterized by high sensitivity to aldose reducta se inhibitors and ability to catalyze the reduction of glucose. Aldose reductase is easily oxidized to a form that is insensitive to aldose reductase inhibitors and unable to catalyze the reduction of glucose. This form does not appear to exist in vivo, even in kidney from diabet ics. There is wide variation in the level of expression of aldose redu ctase in kidney, especially in cortex. The immunochemically separate b ut similar aldehyde reductase is also expressed in kidney as a single enzyme indistinguishable from aldehyde reductase from other human tiss ues. Aldehyde reductase levels exceed those of aldose reductase, both in cortex and medulla.