Effect of Ischemia-Reperfusion Injury on Mitochondrial Malondialdehyde Levels in Kidney Cortex and Medulla of Aged Rats

Background: The present study was undertaken to determine the effect of ischemia-reperfusion injury (IRI) on mitochondrial malondialdehyde (MDA) levels in kidneys from aged rats. MDA is a product of lipid peroxidation of cell and organelle membranes by free radiacals and is used as an indicator of oxidative stress. Kidney dysfunction in ischemia is associated with tissue damage caused by free radicals generated in IRI. Methods: Anesthetized female Lewis rats (22 months of age) were used. Both renal pedicles were clamped for 60 min, followed by 60 min of reperfusion in the Experimental Group (n = 6). The kidneys were then harvested, separated into cortex and medulla, and homogenized. Kidneys in the Control Sham Group (n = 6) were not subjected to IRI before being harvested. The mitochondrial fractions were isolated by differential centrifugation and MDA levels were measured using a spectrophotometric assay. The water content of the cortex and medulla were determined to allow MDA levels to be expressed as nmol/g kidney dry weight. A Student's T Test was used to compare groups, and statistical significance was determined at p< 0.05. All data reported as X ± SEM. Results: MDA levels were not changed in the kidney cortex of the Experimental Group.when compared to the Control Group. Mitochondrial MDA levels in the kidney cortex of the Experimental Group were 19.0 ± 1.8 nmol/ g kidney dry weight and 16.0 ± 1.6 nmol/g kidney dry weight in the Control Group. Mitochondrial MDA levels significantly decreased by 25% in the kidney medulla of the Experimental Group.when compared to the Control Group. Mitochondrial MDA levels of the kidney medulla were 30.5 ± 1.5 nmol/g kidney dry weight in the Experimental Group and 44.5 ± 2.6 nmol/g kidney dry weight in the Control Group. Conclusion: The results suggest that in IRI the mitochondria in both kidney cortex and medulla may not be experiencing increased oxidative stress and damage, as indicated by no change or a decrease in MDA levels, respectively, after 60 min of ischemia.