Regulation of hydrogen peroxide in eye humors. Effect of 3-amino-1H-1,2,4-triazole on catalase and glutathione peroxidase of rabbit eye.

Activities of catalase (H2O2: H2O2 oxidoreductase, EC 1.11.1.6) and GSH peroxidase (GSH: H202 oxidoreductase, EC 1.11.1.9) have been measured in iris, ciliary body, retina, corneal epithelium, corneal endothelium, lens capsule-epithelium and decapsulated lens. 3-Amino-1H-1,2,4-triazole is a specific inhibitor of catalase and a potent cataractogenic agent. We observed marked inhibition of catalase activity in these tissues 1--6 h after the administration of a single intravenous dose of 1 g 3-aminotriazole per kg body weight in rabbit. This was associated with a 2--3-fold increase in the H2O2 concentrations of aqueous humor and vitreous humor. The increased peroxide concentrations were restored to the physiological levels as the catalase activity of eye tissues gradually returned to normal with time after injection. Under the conditions, GSH peroxidase activity of the afore-mentioned eye tissues was unaltered, GSH and protein sulfhydryl of lens were not changed, and ascorbic acid of aqueous humor and vitreous humor was not significantly altered. Based on these findings our conclusion is that catalase of eye tissues regulates the endogenous H2O2 in eye humors to the physiological level. We speculate that H2O2 may be the triggering factor in cataract induced by 3-aminotriazole.