Sugar cataracts in vitro: Implications of oxidative stress and aldose reductase I

The rat lens, when cultured in medium 199 containing 55·5 mm-glucose and 15% fetal calf serum, developed a visible equatorial cortical opacity by the 96th hour. The gerbil lens, whose aldose reductase activity was twice that of the rat lens, developed such an opacity after 24 hr. The development of opacity is thus faster in a lens with higher aldose reductase activity. The relation of aldose reductase with genesis of sugar cataracts is also evident from the observation that substitution of glucose by xylose accelerated cataract formation. Xylose is known to have lower K_m for aldose reductase than glucose. Fortification of the media with vitamin E (2·4 μm) or GSH (0·1 mm) did not prevent the cataract development. The level of lens malonaldehyde, one of the products of lipid peroxidation, was also unaffected either following culture in high sugar media or following in vivo induction of diabetes by streptozotocin. The oxidative stress, thus, does not seem to be involved in initiating the formation of sugar cataracts.