Lipid peroxidation of biological membranes is often implicated in tissue injury. The authors compared the effects of ionic and nonionic contrast media (CM) on the induction of lipid peroxidation in rat kidney and its impact on renal function. Male Wistar rats weighing 200 to 230 grams were dehydrated for 24 hours and divided into 6 groups (n = 15/group). On day 0, groups 1 through 3 were injected with 25% glycerol (10 mL/kg, im) and rats from groups 4 through 6 received an equivalent amount of intramuscular saline. The next day, rats from groups 1 and 4 were injected with normal saline (10 mL/kg, iv); groups 2 and 5 received the ionic CM, diatrizoate, and groups 3 and 6 received the nonionic CM, iopromide. Each CM was tested at 10 mL/kg BW. At 24-hour intervals, 5 rats from each group were sacrificed. In rats injected with CM (diatrizoate or iopromide) alone, no changes in serum creatinine or kidney structure were demonstrated. In glycerol treated rats, a peak in serum creatinine was seen on day 2 which returned to normal level by day 4. Histologic changes included focal tubular damage and intraluminal debris. Malondialdehyde (MDA), a marker of lipid peroxidation concentration was higher than in controls (P less than 0.05). In diatrizoate-injected rats, increase in serum creatinine on day 4 was ten times higher than glycerol; severe morphological alterations in proximal tubules were noted and significant increases in renal MDA concentration were obtained (P less than .05). Iopromide (on day 4), caused a five-fold increase in serum creatinine compared with glycerol.(ABSTRACT TRUNCATED AT 250 WORDS)