Survival rates were not significantly different 5 days after 20-min unilateral ischemia followed by contralateral nephrectomy: 58% in 20-day-old vs. 77% in 55-day-old rats. This experimental approach was used to characterize age dependent differences in the susceptibility of the glutathione system to ischemia and protective effects of treatment with vitamin E (10 mg/100 g b.wt. once daily s.c.) on the outcome after renal ischemia. The degree of postischemic changes (GSH, gamma-GT, TBARS) was the highest on days 1 and 2 after ischemia; at this time, survival rates were similar in young and adult rats. In adult animals, both glutathione content and the activity of gamma-GT were significantly reduced after ischemia whereas in immature rats only the glutathione content was distinctly diminished. At the 5th day after ischemia the parameters were almost normalized in the two age groups. Repeated administration of vitamin E improved the survival rate in adult rats up to 100%; in young animals, lethality was not influenced by vitamin E treatment. This reflects the beneficial effects of vitamin E on the glutathione system in adults whereas the vitamin was without effect on the immature rats' glutathione system.