Background: Ureteral obstruction, leading to urinary stasis and elevated pressure in the proximal part of urinary tract, causes progressive renal dysfunction. This study was designed to evaluate the status of oxidative stress and metabolic defect in acute unilateral ureteral obstruction (UUO).

Methods: Experiments were performed on three groups of male Sprague-Dawley rats (n=10 in each group). In the UUO group, rats were lightly anesthetized by ether and the left ureter was occluded by means of a sterile surgical procedure. Twenty-four hours after UUO-induction, both kidneys were removed and stored at -70 °C. In the sham group, anesthesia and surgery were performed without ureteral occlusion, and the control group received no surgical procedure. The kidney samples were assessed to measure the levels of ATP and ADP by the luciferin-luciferase method for determining metabolic status. In addition, the levels of malondialdehyde (MDA) and ferric reducing/antioxidant power (FRAP) of the kidneys were measured to evaluate the redox state. Data are expressed as means ±SEM per gram of kidney weight (gKW). The comparisons were performed using paired t-test for intra-group analysis, and ANOVA followed by Duncan's post-hoc test and then LSD test for inter-group analysis. Significance was taken at p<0.05.

Results: The comparisons between the UUO and sham groups indicated that 24 hours of UUO increased levels of MDA (51.42±1.86 vs. 38.64±1.02 nmol/gKW, respectively; p<0.001) and ADP (0.67±0.04 vs. 0.47±0.045 µmol/gKW, respectively; p<0.01), but decreased levels of FRAP (2.44±0.18 vs. 4.28±0.27 µmol/gKW, respectively), ATP (1.09±0.10 vs. 2.26±0.19 µmol/gKW, respectively) and ATP/ADP ratio (1.64±0.14 vs. 5.11±0.56, respectively) in the obstructed kidneys, all p<0.001. In the non-obstructed kidneys, the levels of ATP and ADP were higher (p<0.01 and p<0.001, respectively), while the levels of MDA and ATP/ADP ratio were equal to those of the sham group.

Conclusion: Twenty-four hours of acute UUO induces oxidative stress and reduces the aerobic metabolism in obstructed kidneys, whereas non-obstructed kidneys with a normal redox state show the higher levels of metabolism.