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Hydrogen peroxide removal by the calf aqueous outflow pathway
K P Nguyen1, M L Chung, P J Anderson
1Howe Laboratory of Ophthalmology, Massachusetts Eye and Ear Infirmary, Harvard Medical School, Boston 02114.
Investigative Ophthalmology & Visual Science
|June 1, 1988
Summary
The eye's outflow pathway effectively removes hydrogen peroxide (H2O2), reducing its concentration significantly. Inhibitors like 3-aminotriazole partially block this removal, indicating the pathway's role in H2O2 homeostasis.
Area of Science:
- Ophthalmology
- Biochemistry
- Physiology
Background:
- Aqueous humor in calf and human eyes contains approximately 25 microM hydrogen peroxide (H2O2).
- The removal mechanisms of H2O2 within the eye are not fully understood.
Purpose of the Study:
- To investigate the removal of hydrogen peroxide (H2O2) by the aqueous humor outflow pathway in calf eyes.
- To assess the impact of inhibitors on H2O2 removal by ocular outflow structures.
Main Methods:
- Intact, enucleated calf eyes were perfused with media containing varying concentrations of H2O2 and inhibitors.
- Silicone oil was used to collect perfusate from the anterior chamber and aqueous veins.
- H2O2 concentrations were measured in the anterior chamber and perfusate.
- Lactate dehydrogenase (LDH) activity was assessed to evaluate tissue damage.
Main Results:
- The outflow pathway significantly reduced H2O2 concentration (150-1000-fold) at 5 mM.
- 3-aminotriazole inhibited H2O2 removal by approximately 50% at 80 mM.
- Higher H2O2 concentrations (≥10 mM) or certain inhibitor combinations (BCNU, diamide, 3-aminotriazole) caused significant cell damage, indicated by a 30% drop in LDH activity.
Conclusions:
- The eye's outflow pathway plays a crucial role in clearing hydrogen peroxide (H2O2).
- Enzymatic processes, potentially involving catalase inhibited by 3-aminotriazole, contribute to H2O2 removal.
- High concentrations of H2O2 or specific inhibitors can compromise the integrity of ocular outflow tissues.