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

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.

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.

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 alphaA- and betaB1-crystallins in the soluble fraction and aggregation of alphaA-crystallin, in addition to the degraded fragment of betaB1-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 alphaA-crystallin.

The results of this study suggest that there is loss, as well as aggregation, of alphaA-crystallin in the aging rat lens, although there is no accompanying loss of lenticular transparency.