Lipid peroxidation assessment of free radical production following release of obstructive uropathy

Purpose: To identify if free radicals were released following relief of ureteric obstruction. Materials and Methods: Free radical production was assessed by a high performance liquid chromatography assay of malondialdehyde (MDA) in a 24-hour complete unilateral ureteric obstruction model in Wistar rats. Results: In the first experiment, a rise greater than 20% above prerelease levels in renal venous malondialdehyde levels was observed at 8, 15, 22, and 30 minutes following release. At 45 and 60 minutes, levels were similar to the prerelease levels. In the second experiment, renal venous samples taken before release and at 10 and 20 minutes after release in control and obstructed groups (n = 7) identified a significant difference (T = 10 minutes p = 0.006 and T = 20 minutes p = 0.045). A significant MDA rise following release occurred only in the obstructed group (obstruction group: MDA level T = 0 min. 1.01 mu mol./l. +/- 0.13, T = 10 min. 2.12 mu mol./l. +/- 0.3 p = 0.016, T = 20 min. 2.09 mu mol./l. +/- 0.28 p = 0.016. Control group: T = 0 min. 1.13 mu mol./l. +/- 0.23, T = 10 min. 1.05 mu mol./l. +/- 0.18 p = 0.95, T = 20 min. 1.23 mu mol./l. +/- 0.19 p = 0.67). In the third experiment, an attempt was made to block free radical release with allopurinol. No statistical difference between the control and obstructed groups with allopurinol was noted at 20 minutes after release. A Kruskal Wallace two-way analysis identified a significant difference between experiments two and three at both time periods (p = 0.049). Conclusion: This study suggests, for the first time, that free radicals are released after relief of ureteric obstruction and that this release is partially attenuated by allopurinol pretreatment.