PROTEOLYSIS BY CALPAIN IS AN UNDERLYING MECHANISM FOR FORMATION OF SUGAR CATARACT IN RAT LENS

To confirm the effect of a new choice aldose reductase inhibitor (ARI) , rat lenses were cultured with xylose. ARI prevented opacities and re duced lens hydration caused by xylose. Next, cataract was produced by feeding a diet containing 50% galactose. ARI was tested for ameliorati on of cataract. On day 19 after feeding of galactose, nuclear cataract s were visible in 75% of the animals receiving only galactose, while n uclear cataracts were not observed in animals treated with ARI. In gal actose cataract, lens hydration and calcium were significantly increas ed. Calpain in soluble and insoluble fractions was decreased. alpha- a nd beta-crystallins were proteolyzed. These changes were inhibited by administration of ARI. These results suggested that proteolysis by cal pain is an underlying mechanism in formation of sugar cataract in rat lens.