Modelling cortical cataractogenesis VII: Effects of vitamin E treatment on galactose-induced cataracts.

The possibility that vitamin E or other antioxidants might prevent cataracts was tested by incubating rat lenses in vitro in galactose-enriched medium or by treating rats fed a diet containing 50% galactose (w/w). The vitamin E was added to the medium at 2.4 microM, and to the diet at a level of 5 g kg-1 diet. In vitro, lenses incubated with 55.6 mM galactose underwent globular degeneration, which was partially prevented by addition of vitamin E (2.4 microM). Even in such vitamin E-protected lenses, which appeared clear, many small globules could be seen in the region of interdigitation at the 'corners' where hexagonal cells intersected. In vivo, in dietary experiments, a dense nuclear opacity of the lens was observed after approximately 5 weeks; unlike diabetic cataracts, this was not prevented by the addition of vitamin E to the diet. The extensive globular degeneration observed was typical of that found in long-term (21-week diabetic) cataracts. Although no significant difference in cataract incidence was observed, the extent of damage in vitamin E-treated rat lenses appeared to be less. The difference in effectiveness of vitamin E in galactose-induced cataracts, as compared to diabetic cataracts, is tentatively ascribed to (1) the more severe osmotic stress expected from the products of the aldose reductase pathway for galactose and (2) the greater depletion of reduced pyridine nucleotides (NADPH + NADH) expected of galactose as compared to glucose.