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Lens GSH depletion and electrolyte changes preceding cataracts induced by buthionine sulfoximine in suckling mice
H I Calvin1, S von Hagen, J L Hess
1Department of Ophthalmology, Biochemistry and Molecular Biology, UMD-NJ Medical School, Newark 07103.
Abstract:
Cataracts were induced in suckling mice by multiple injections of L-buthionine-S,R-sulfoximine (BSO), a specific inhibitor of GSH biosynthesis, starting on post-natal day 7. The earliest visible lens aberrations began approximately 2 days after t(o), following 99% depletion of lens GSH. Cataract development then proceeded through four stages within less than 24 hr. Elevated Na+ and Ca+ and decreased K+ were first detected in pre-cataractous (stage 0) lenses. During stage 0, lens Na+ and K+ levels displayed a significant inverse correlation; by contrast, Ca2+ levels were poorly correlated with those of Na+. The initial increase in Na+ exceeded the decrease in K+. This suggested the presence of osmotic stress prior to cataract stage 1 (developing floriform). Increased lens hydration was first apparent in stage 1, coincident with a marked elevation of Ca2+, further increase in Na+ and decrease in K+. These trends persisted in the stage 2 cataract (completed floriform). Subsequent changes in lens hydration and cation content during cataract stages 3 (degenerate floriform) and 4 (amorphous translucent) suggested substantial influx of extracellular fluid into the affected lenses. The BSO cataract may represent a useful in vivo model to study the functions of GSH in maintaining normal lens cation balance and transparency.
Insights
This study used L-buthionine-S,R-sulfoximine (BSO) to induce cataracts in mice, revealing significant changes in lens cation balance and hydration during cataract development. The findings highlight the role of glutathione (GSH) in maintaining lens transparency.
Area of Science:
- Ophthalmology
- Biochemistry
- Cell Biology
Background:
- Glutathione (GSH) is crucial for maintaining lens transparency and normal cation balance.
- Inhibiting GSH biosynthesis can lead to cataract formation.
- Understanding the biochemical changes during cataractogenesis is vital for developing treatments.
Purpose of the Study:
- To investigate the in vivo effects of GSH depletion on lens cation homeostasis and hydration.
- To characterize the stages of cataract development induced by L-buthionine-S,R-sulfoximine (BSO).
- To establish BSO-induced cataracts as a model for studying GSH function in the lens.
Main Methods:
- Cataracts were induced in suckling mice using multiple injections of L-buthionine-S,R-sulfoximine (BSO).
- Lens GSH levels were monitored, alongside measurements of sodium (Na+), potassium (K+), and calcium (Ca2+) concentrations.
- Lens hydration and visual aberrations were assessed during cataract progression.
Main Results:
- BSO induced rapid cataract development following 99% depletion of lens GSH.
- Pre-cataractous lenses showed elevated Na+ and Ca2+, decreased K+, and osmotic stress.
- Cataract stages were characterized by progressive cation imbalance, increased hydration, and eventual extracellular fluid influx.
Conclusions:
- BSO-induced cataracts provide a valuable in vivo model for studying GSH's role in lens physiology.
- Lens cation balance and hydration are critically dependent on adequate GSH levels.
- Disruptions in GSH biosynthesis lead to significant alterations in lens ion transport and osmotic regulation, resulting in cataract formation.