DIFFERENTIAL-EFFECTS OF GALACTOSE-INDUCED CATARACTOGENESIS ON THE SOLUBLE CRYSTALLINS OF RAT LENS

Soluble lens crystallins from 6-10-week-old, galactose-fed, male Sprague-Dawley rats were analyzed by two-dimensional polyacrylamide gel electrophoresis at each of the five Sippel stages of cataractogenesis. Electrophoretograms were compared with similarly analyzed crystallins from comparably aged, chow-fed controls. Polypeptides were assigned to crystallin families and subfamilies on the basis of chromatographic fractionations with Sephadex G-200, superfine. Staining intensities of polypeptides from control lenses remained essentially unchanged throughout the experimental period, while those of the polypeptides from cataractous lenses showed non-uniform changes. Staining of the genomic γ-crystallins increases up to at least stage 3; by stage 4, staining of γ-chains, with perhaps those of γ5 and γ6 excepted, diminishes and in the total cataract, staining of all chains is further reduced. With possibly the addition of one chain, the total number of postsynthetically modified γ-crystallins in cataractous lenses does not exceed that in the comparably aged normal lens. The genomic α- and β-crystallin polypeptides are sustained close to normal levels up to stages 3 or 2. respectively, after which their gradually falling levels are accompanied by the generation of new species or elevated levels of existing post-translational species. An exception to this behavior is the rapid and total loss of βB1a, a genomic subunit implicated in the aggregation of βH-crystallins. Charge heterogeneity and variable pl displayed by βB1a and other highly cationic β- and γ-crystallin polypeptides can be induced during isoelectric focusing and may be due to thiol group oxidation. © 1990.