Hyperbaric Oxygen Inhibits the Growth of Cultured Rabbit Lens Epithelial Cells Without Affecting Glutathione Level

Studies on human patients and experimental animals indicate that hyperbaric O 2 can opacity the lens nucleus and damage the lens epithelium in vivo. Here we investigate the effects of hyperbaric O 2 on cultured rabbit lens epithelial cells (LECs). When the cells were exposed to 50 atm O 2 (99% O 2 + 1% CO 2) for 3 hr there were no immediate effects on morphology, viability and transport processes (uptake of 86 Rb and 14C-αAIB). In addition, the O 2 treatment did not lower the high level of reduced glutathione or increase the low level of oxidized glutathione. However, 50 atm O 2 did produce a near doubling in the glycolytic rate which maintained ATP at levels only slightly lower than normal. Although the 3-hr O 2 treatment was not lethal, it completely inhibited cell division for 2 days. After 2 days, growth was initiated and, at day 7 the rate of growth was faster than the controls (control cells were treated with ambient air or 50 atm N 2 for 3 hr). Cells treated with 8 atm O 2 for 3 hr exhibited a slowed rate of growth, relative to controls, while exposure to 2 atm O 2, did not inhibit mitosis. Changes in morphology (multilayering and elongation) of cells exposed to 50 atm O 2, but not the controls, were evident 7 days after the 3-hr exposure. The incorporation of [ 35 S]methionine into individual polypeptides and [ 3H]thymidine into DNA was significantly inhibited immediately following a 3-hr treatment with 50 atm O 2, but both parameters recovered within 2 days. DNA strand breaks were observed in LECs following hyperbaric O 2 treatment as low as 4 atm O 2 for 3 hr and increased with higher pressures of O 2, but not N 2. Treatment with 50 atm O 2 nearly doubled the activity of the DNA repair enzyme, poly-ADP-ribose polymerase, and decreased the level of its substrate NAD +; the latter effect was reduced by 3-aminobenzamide, an inhibitor of the enzyme. Thus, although LECs tolerated brief exposures to high pressures of O 2 without cell death, DNA damage occurred at relatively low pressures of O 2. All of the effects of hyperbaric O 2 on LECs occurred without any alteration of the normal levels of reduced and oxidized glutathione. It appears that GSH is important in maintaining cell viability during exposure to an elevated level of O 2, but that it is incapable of preventing O 2-induced effects on growth and DNA.