Biochemical changes in urine and plasma of rats in food chain-mediated cadmium toxicity

The present study sets out to assess the toxicity of cadmium (Cd) administered via the food chain. The food chain was mimicked by exposing rats to diet containing milled Cd-exposed catfish as the source of protein. The toxicity of Cd was monitored by the determination of indices of oxidative stress and kidney dysfunction in plasma and urine of the rats after 1- and 3-month exposure periods. The results obtained indicate that Cd exposure in the rats was followed by marked accumulation of the metal in the liver and kidney with time. However, the kidney accumulated more Cd relative to the liver after both exposure periods. The levels of glucose, creatinine and lipid peroxidation were significantly (p < 0.05) increased in both plasma and urine of the rats after 1 month of exposure. Conversely, rats fed the test diet for 3 months had significantly (p < 0.05) decreased level of lipid peroxidation in the plasma and urine. However, the plasma and urine glucose concentrations were restored to levels not significantly (p > 0.05) different from control in rats fed the test diet for 3 months. Similarly, after 3 months, the creatinine level in the plasma was also restored to a level not significantly (p > 0.05) different from that of the control but was significantly (p < 0.05) elevated in the urine. A significant increase in urine protein concentration was demonstrated after 1-month exposure to Cd, but no significant change occurred in the plasma. Rats fed diet containing the Cd-incorporated fish for 3 months also had no significant (p > 0.05) change in plasma and urine protein concentrations. These results suggest that this route of exposure caused kidney impairment, oxidative stress as well as alteration in glucose metabolism after 1 month but not after 3 months, possibly due to adaptation occasioned by the antioxidative defense armory of the rats.