THE REACTION OF MALONDIALDEHYDE WITH LENS PROTEINS AND THE PROTECTIVEEFFECT OF ASPIRIN

Malondialdehyde, a product of lipid peroxidation and a by-product of t hromboxane synthesis increases in human cataract. Malondialdehyde boun d to soluble lens proteins over 4 h of incubation. Pre-incubation of l ens proteins with aspirin offered protection against reaction with MDA . Gel chromatography was used to monitor aggregation of the modified p rotein. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis show ed that the reaction with malondialdehyde led to non-disulphide covale nt cross-linking of gamma-crystallin, which was decreased by incubatio n with aspirin. Malondialdehyde has two carbonyl groups which could re act with primary amino groups, forming Schiff-base congugates and cova lently cross-link proteins. The modification and cross-linking could i nitiate the cataractogenic process.