CORRELATION OF PHOSPHOLIPID HYDROPEROXIDE GLUTATHIONE-PEROXIDASE ACTIVITY TO THE SENSITIVITY OF RAT RETINAS TO PHOTIC INJURY

We hypothesize that the differential susceptibility to photic njury am ong different strains of rat retinas may depend on the levels of phosp holipid hydroperoxide glutathione peroxidase (PHGPX) activity, one of the endogenous antioxidant enzymes in the retina. The retinas of four inbred strains of albino rat (Fischer, Wistar, Buffalo and Lewis) were analyzed for glutathione peroxidase activity using H2O2, cumene hydro peroxide, and phospholipid hydroperoxide as assay substrates. In all f our strains of rat, PHGPX was observed only in the high salt extract o f the retina, while peroxidases determined by H2O2 Or cumene hydropero xide were observed mainly in the low salt extract. PHGPX was highest ( 66.7 mU/mg) in the most light-resistant Fischer strain and lowest in t he most light-sensitive Lewis strain (31.9 mU/mg), while the activity levels in the moderately light-sensitive Buffalo and Wistar strains we re 46.6 and 38.5 mU/mg, respectively. In contrast, there was no signif icant difference in peroxidases determined by H2O2 or cumene hydropero xide among the four strains. These observations suggested that, in rat retina, the membrane-associated PHGPX may have an important role in t he defense against light-induced free radical damage.