Evaluation of long-term effects of nickel and benzo [a] anthracene contaminated diets in rats' kidney; mimicking human exposure from food.

Abstract

Objectives: Accumulative effects of heavy metals and polycyclic aromatic hydrocarbon could result in various toxicities. This study evaluated the effects of long-term exposure to low doses of nickel and benzo [a] anthracene on the kidney of rats, simulating human exposure through food.

Methods: Thirty-six (36) Male rats weighing between 80-100 g were assigned into six groups of 6 animals each; Group A (normal), Group B1 and B2 (fed nickel contaminated feed for 12 and 24 weeks), Group C1 and C2 (fed benzo [a] anthracene contaminated feed for 12 and 24 weeks). Blood and kidney of the rats were harvested after animal sacrifice. Serum creatinine and urea concentration and renal Superoxide Dismutase (SOD) activity, GSH, MDA, protein carbonyl, and total protein concentration by spectrophotometric methods. While the concentration of 8-oxodeoxyguanosine in kidney was determined by ELISA method and protein carbonyl by colorimetric method. Renal histological analysis was done with H and E staining. Statistical analysis was performed with Statistical Package for Social Sciences (SPSS) and statistical significance was accepted 95 percent confidence level.

Result: From the results, urea concentration increased significantly (P<0.05) in the nickel exposed group after 24 weeks exposure whereas creatinine concentration increased significantly (P<0.05) after 12 weeks of exposure when compared with the control. Comparison of the serum urea and creatinine level of the benzo [a] anthracene exposed group with the control showed no significant (P>0.05) difference. Histological observations indicate glomerular atrophy and widened capsular space haemorrhagic areas, visceral and parietal layer of the Bowman's capsule, the proximal convoluted tubule in the nickel exposed group while the kidney of benzo (a) anthracene exposed rats showed deviation in the histo-architecture of the renal parenchyma as evidenced by glomerular atrophy and widened Bowman's capsular space and focal haemorrhagic areas. Protein thiol level and Superoxide dismutase activity was significantly (P<0.05) depleted in the benzo [a] anthracene exposed groups. The levels of total protein, protein carbonyl, and 8-oxodeoxyguanosine were significantly (P<0.05) elevated in the nickel and benzo [a] anthracene exposed groups.

Conclusion: This study demonstrated the oxidative stress causing effects of benzo [a] anthracene and nickel in the kidney. It also shows that consistent exposure to low doses of the contaminants for a lifetime might result in renal oxidative stress with consequential loss of renal function.