Alterations in lenticular proteins during ageing and selenite-induced cataractogenesis in Wistar rats

PURPOSE: To determine putative alterations in the major lenticular proteins in Wistar rats of different ages and to compare these alterations with those occurring in rats with selenite-induced cataract. METHODS: Lenticular transparency was determined by morphological examination using slit-lamp biomicroscopy. Alterations in lenticular protein were determined by sodium dodecyl sulfate-PAGE (SDS–PAGE) and confirmed immunologically by western blot. RESULTS: Morphological examination did not reveal observable opacities in the lenses of the rats of different age groups; however, dense nuclear opacities were noted in lenses of rats in the selenite-cataract group. Western blot assays revealed age-related changes in soluble and urea-soluble lenticular proteins. Decreased αA- and βB1-crystallins in the soluble fraction and aggregation of αA-crystallin, in addition to the degraded fragment of βB1-crystallin, in the urea-soluble fraction appeared to occur in relation to increasing age of the rats from which the lenses were taken; similarly, cytoskeletal proteins appeared to decline with increasing age. The lenses from rats in the selenite-cataract group exhibited similar changes, except that there was also high molecular weight aggregation of αA-crystallin. CONCLUSIONS: The results of this study suggest that there is loss, as well as aggregation, of αA-crystallin in the aging rat lens, although there is no accompanying loss of lenticular transparency.