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Opacification of isolated rat lenses intoxicated with diethylmaleate: relation to lens membrane dysfunction
1Department of Chemistry, School of Medicine, Fujita Health University, Toyoake, Japan. yohta@fujita-hu.ac.jp
Abstract:
We examined whether opacification of rat lenses treated with diethylmaleate (DEM), a depletor of reduced glutathione (GSH), is associated with membrane dysfunction. When isolated rat lenses were incubated with 2 mM DEM for 1, 6, and 24 h, a cortical opacity appeared at 6 h and was more pronounced at 24 h. This opacification was accompanied by decreases in GSH and vitamin E (Vit. E) content and Na+,K+-ATPase activity, and an increase in water content, but not by a change in the content of thiobarbituric acid reactive substances (TBARS), an index of lipid peroxidation. Vit. E co-treatment caused a partial prevention of opacification, a complete recovery of decreased Vit. E content, attenuation of decreased Na+,K+-ATPase activity, and a decrease in TBARS content in rat lenses treated with 2 mM DEM for 24 h. Neither opacity formation nor changes in Vit. E, TBARS, and water content and Na+,K+-ATPase activity occurred in rat lenses treated for 48 h with 2 mM l-buthionine-(S,R)-sulfoximine, an inhibitor of glutathione synthesis, although a marked GSH depletion was observed. These results suggest that opacification of isolated rat lenses treated with DEM could be associated with impairment of Na+,K+-ATPase rather than GSH depletion.
Insights
Diethylmaleate (DEM) causes rat lens opacification linked to membrane dysfunction, specifically Na+,K+-ATPase impairment, not lipid peroxidation. Vitamin E partially prevents opacity and restores enzyme activity, suggesting its protective role.
Area of Science:
- Ophthalmology
- Biochemistry
- Cell Biology
Background:
- Cataract formation involves complex biochemical changes in the eye lens.
- Reduced glutathione (GSH) depletion is implicated in lens opacification, but the precise mechanisms remain unclear.
- Membrane dysfunction and oxidative stress are potential contributors to cataractogenesis.
Purpose of the Study:
- To investigate the association between diethylmaleate (DEM)-induced rat lens opacification and membrane dysfunction.
- To determine the role of reduced glutathione (GSH) depletion and lipid peroxidation in this process.
- To evaluate the protective effects of vitamin E (Vit. E) against DEM-induced lens changes.
Main Methods:
- Isolated rat lenses were incubated with DEM (2 mM) for varying durations (1, 6, 24, 48 h).
- Biochemical assays measured GSH, vitamin E, thiobarbituric acid reactive substances (TBARS), and water content.
- Na+,K+-ATPase activity was assessed.
- Lenses were co-treated with vitamin E or l-buthionine-(S,R)-sulfoximine (GSH synthesis inhibitor).
Main Results:
- DEM treatment led to cortical opacification, decreased GSH and vitamin E, reduced Na+,K+-ATPase activity, and increased water content.
- Opacification and membrane dysfunction occurred without significant lipid peroxidation (TBARS).
- Vitamin E co-treatment partially prevented opacification and restored Na+,K+-ATPase activity.
- GSH depletion by l-buthionine-(S,R)-sulfoximine alone did not cause opacification or membrane dysfunction.
Conclusions:
- DEM-induced rat lens opacification is associated with impaired Na+,K+-ATPase activity, suggesting membrane dysfunction is a key factor.
- GSH depletion alone is insufficient to cause opacification; membrane integrity is crucial.
- Vitamin E exhibits protective effects against DEM-induced lens opacification and membrane damage.