[Change in peroxidation and in the phospholipid content in the brain in hyperoxia and the protective action of urea].

The rate of lipid peroxidation (by content of the lipid peroxide transformation end product--malonic dialdehyde) in homogenates of rat brain was studied as affected by hyperoxia and with a protective effect of urea in experiments in vivo and in vitro. In both cases an increase is observed in the malonic aldehyde yield with the effect of oxygen under higher pressure. Urea in physiological concentrations lowers the yield under the effect of hyperoxia in vitro. In experiments in vivo introduction of urea also evokes a decrease in the rate of peroxidation. It is established that hyperoxia and urea affect mainly the ascorbate-dependent system of peroxidation. The compositon of phospholipids in the rat brain was studied under the effect of hyperoxia and urea. No changes were found in the number of fractions under the effect of 6at oxygen, only quantitative changes are observed. With introduction of urea before hyperoxia there occurs a normalization in the phospholipid composition. The authors suppose the protective effect of urea to be due to its influence on membranes.