Protein-
thiol mixed
disulfides in
lenses have been implicated in the mechanism of
protein-
protein disulfide and other cross-linking leading to
protein aggregation. The methodology for the detection and quantitation of
protein-
thiol mixed
disulfides has been successfully established in our laboratory. Examination of mixed
disulfides at different stages during development of a
cataract may give relevant information on the mechanism of cataractogenesis, and whether oxidation is a part of that mechanism. In this study we investigated the involvement of mixed
disulfides in
cataract formation by using the H2O2-exposed lens as a model. Rat
lenses, after being exposed to 0.5 mM H2O2 in culture showed an inverse relationship between the GSH loss and the
protein-GSH formation with no effect on the
protein-
cysteine level. The H2O2-induced
protein modification was also demonstrated indirectly by isoelectric focusing. The rate of
protein-GSH production is dependent on the time of exposure and the concentration of H2O2. Age also plays some role as the lens GSH level decreases and the
protein-
thiol mixed
disulfides increase as the animal becomes older.
Lenses of older rats did not display more susceptibility to H2O2-induced mixed
disulfide formation. The two
protein-
thiol mixed
disulfides have a well-defined pattern of distribution in the rat lens. Most of the
protein-GSH was found in the cortex and the water-soluble
protein fraction whereas more
protein-
cysteine was found in the nucleus and water-insoluble
protein fraction. Lens of older rat has more
protein-
cysteine as well as more water-insoluble
proteins.(ABSTRACT TRUNCATED AT 250 WORDS)