Study Of Oxidative Stress And Hepatocellular Injury Induced By Oral Administration Of Trivalent Chromium In Chicken

In nature, chromium(Cr) has "-2" to "+6" valence states, but "+3" and "+6" are the most common valence states. Cr6+ as the most toxic is often combined with oxygen to produce chromate and dichromate. It is a strong oxidant, which can be easily reduced to trivalent chromium in acidic solution. Cr3+ is the most stable oxidation state. It has the highest biological activity and the smallest toxicity. It is integrant to the organism as the most stable and the most common element. However, professor Liu et al. study also showed that high dose of Cr3+(more than 2500mg·kg-1) would break the storage and regulatory capacity of Cr3+, resulting in a sharp rise in blood Cr3+ content and interference with other nutrients such as iron, zinc, manganese, calcium and so on. Sobol and Schiestl had also demonstrated that the Cr3+ could result in DNA damage due to DNA oxidation damage and the interaction of Cr3+- DNA.To further investigate the oxidative toxicity of Cr3+, we administered the Hailanhe male chicken in different doses of CrCl3 solutions(1/2 LD50,1/4 LD50,1/8 LD50) and equivalent water orally. They were also named high, medium, low and control group. Chicken liver samples were measured by colorimetric method for the activities of antioxidant enzymes(GSH-PX, CAT, T-SOD), the contents of glutathione, total antioxidant capacity(T-AOC), malondialdehyde(MDA), and hydrogen peroxide(H2O2) as well as the histological analysis to indirectly evaluate the oxidative stress in chicken liver. Results indicated that the oral administration of Cr3+ at high dose significantly increased(P < 0.05) the MDA levels after 28 days of exposure, with decreased T-AOC, glutathione, and antioxidant enzymes activities. Low and medium doses groups show that T-AOC, glutathione, and antioxidant enzymes activities increased after 14 days, then decreased gradually, but low and medium groups higher than control group, only high group lower than control group finally. Besides, in the normal liver section of the control group, the hepatic cords were closely arranged, with a polygonal shape and normal space, The histologic sections of the medium group slightly changed, only vacuolar degeneration occurred between the hepatic cords, while in high-dose group hepatic cords were loosely arranged, and the focal inflammatory cells were dispersed in hepatic cords and gathered in infiltrated neutrophils. These statistics and histopathological analysis suggest that high dose and long-term exposure of Cr 3+ induce oxidative stress and hepatocellular injury.