HYDROGEN-PEROXIDE AFFECTS SPECIFIC EPITHELIAL SUBPOPULATIONS IN CULTURED RABBIT LENSES

Purpose. To investigate the effect of hydrogen peroxide on the epithel ial cells of cultured rabbit lenses. Methods. Lenses were cultured in minimum essential medium containing a single dose of 0.03, 0.1, or 0.2 mM H2O2. Three hours later the medium was replaced with peroxide-free minimum essential medium. Lenses were also treated with 0.5 mM 1,3-bi s(2-chloroethyl)-1 nitrosourea (BCNU) to lower the activity of glutath ione reductase and then exposed to 0.03 mM H2O2 maintained nearly cons tant by glucose oxidase. After H2O2 treatment, lenses were fixed and w hole mounts of the epithelium were prepared or lenses were processed f or electron microscopy.Results. Cells exposed to a single dose of 0.03 mM H2O2 appeared normal; 0.1 mM H2O2 was not cytotoxic. Exposure to 0 .2 mM H2O2 elicited swelling in cells in the pre-equatorial region (30 minutes) followed by the formation of islands of cells in the pre-equ atorial region at 1 hour. Central epithelial cells appeared normal at 1 hour, were swollen at 3 hours and dead at 24 hours. By 48 hours, dea d cells were found in the pre-equatorial and central regions. Cells in the peripheral region of the epithelium did not exhibit cytotoxicity. If lenses were pretreated with BCNU and then challenged with a mainta ined level of 0.03 mM H2O2, cytotoxicity was induced in the central an d pre-equatorial regions. Cells in the peripheral region survived BCNU -H2O2 treatment. Conclusions. Cells in the peripheral region of cultur ed lenses were more resistant to H2O2 cytotoxicity than cells in the c entral and pre-equatorial regions. The antioxidant defense or repair s ystems for H2O2-induced damage do not appear to be uniformly distribut ed in subpopulations of the lens epithelium.