Oxygen Production by Dogfish (Mustelus canis) Cornea and Lens Catalase In Situ

Only catalase produces molecular oxygen from H202. Its antioxidant action (i.e., HzOz detoxification) represents the end reaction in the redox enzyme chain. It thus defends cells against oxidation that ultimately leads to cytotoxicity. Catalase activity (i.e., the ability to convert H202 into O2 in the epithelial cells of the dogfish lens) is inhibited by UVA irradiation (1, 2), and this causes lens opacification. We have examined the catalase activities of the corneas and lenses of intact dogfish eyes. We have also exposed the anterior segments ofdogfish eyes to UVA and studied the effect of this treatment on the catalase activity of the cornea and lens. We have measured catalase activity when [O,] is markedly reduced. Oxygen production from HzOz by the anterior surfaces of corneas and lenses was measured with an O2 electrode and meter (Microelectrodes, Inc.). Fresh eyes were trimmed and washed with elasmobranch Ringers solutions. “Krazy glue” (cyanoacrylate) was used to attach a plastic cylinder about 1 cm diameter and 1.5 cm in height to the central anterior surface of the cornea, and to the anterior surface of the lens (i.e., with the cornea removed). The cylinder-fixed in this way to the tissue-formed a cup into which was added about 1 ml of Ringers medium. A calibrated O2 electrode (2 1% O2 in HzO) was inserted into the cup, and the increase in O2 per min was recorded. Purified beef liver catalase (Sigma) was the standard. The increase in % O*/min due to the reaction of HzOz with catalase was determined from a standard curve. This curve was linear between 1.2% O*/min and 4% 02/min. Table I indicates that the cornea and lens produce O2 at 1.55 f 1 .O 1 and 2.80 f 1.42% O2 per mitt, respectively. 3-amino-triazole (25 mm, a strong catalase inhibitor) totally prevented the catalase activities of lens and cornea. After 130 J/cm* of UVA irradiation of the eyes, catalase activities were totally inhibited in both the cornea and lens (after cornea removal). When the O2 concentration in cups containing 0.6 ml of Ringers was reduced to ~2% with Nz, and 0.3 ml of N,-flushed 0.39 mM HzOz was added, corneas and lenses produced O2 at 0.79% and 1.73% per min, respectively. Solutions with Nzflushed H202 but no tissues, or tissues bathed only with Ringers, did not regain O2 for at least 3 to 5 min, proving that the O2 was produced by the cornea and lens catalase. This finding