Thiol disulfide exchange modulates the activity of aldose reductase in intact bovine lens as a response to oxidative stress

The reversibility of S-thiolation of aldose reductase was shown in intact b ovine lens Subjected to oxidative stress. The glutathione modified aldose r eductase generated in the lens as a consequence of hyperbaric oxygen treatm ent was recovered in its reduced form following culturing in normobaric air conditions. Nucleus and cortex were differently affected by both oxidative treatment and normobaric air recovery The extent of S-thiolation of aldose reductase appeared to be higher in the nucleus than in the cortex. Moreove r, the nucleus, but not the cortex, was unable to completely recover from t he protein S-thiolation process. The ratios of GSH/GSSG and NADPH/NADP(+) a s well as the Energy Charge values were determined in the cortex and nucleu s both after oxidative stress and recovery. The results are consistent with the existence of a quite well-defined boundary between the two lens region s. Moreover, they are supportive of the hypothesis that thiol/disulfide exc hange has the potential to be a regulatory mechanism for certain enzymes wh ich can modulate the flux of NADPH inside the cell. (C) 2000 Academic Press .