Oxidative Stress And Hepatocellular Injury Induced By Of Cr⁶⁺ In Chicken

Hexavalent chromium Cr(VI) and its compounds are one of the most common heavy metal pollutants in the environment. Water with chromate has become more and more serious pollution in the environment since chromate and chromium compounds are widely used in industry. Recently, several reports indicated that people who worked in the environment with chromate for long time were diagnosed cancer and other kinds of diseases. Many researches showed that hexavalent chromeium can be transported to many organs in the body via the blood current after entering into the body. It is known widely that the liver is the target organ for detoxification and metabolism. However, the function and structure of liver cells could be damaged after chromium poisoning. Researches showed that hexavalent chromium can damage the structure of mitochondria in the liver leading to cell necrosis. Moreover, the blood biochemical indicators and antioxidant activities can help to evaluate the damage degree in practice. So in this study different concentrations of hexavalent chromium were added into drinking water to research the influence of hexavalent chromium in the liver of chickens.This study is aimed to evaluate oxidative stress and hepatotoxicity induced by potassium dichromate in chickens via drinking water. Hy-Line Brown chickens were used to pre-test and the acute toxicity experiment was conducted by gavage firstly. By observing the chicken’s clinical symptoms and pathological changes, the toxicity of potassium dichromate to the chickens was determined. The chicken’s median lethal dose(LD50) of potassium dichromate was calculated by the method of Horn(LD50=0. 501 g kg-1). Seventy-two Hyland Brown Chickens were randomly divided into 4 groups(24 chickens each group): control group, low-dose(2% LD50) Cr(VI) group, middle-dose(6% LD50) Cr(VI) group, high-dose(10% LD50) Cr(VI) group. Potassium dichromate was given orally via drinking water to the chickens for 42 days body weight daily respectively; the control group was treated with the same volume of distilled water. The exposure time was 14 days, 28 days and 42 days respectively. The blood biochemical indicators were assessed to determine the effects of different concentrations of hexavalent chromium in the liver of chickens. The activities of the superoxide dismutase(SOD) and glutathione(GSH) and the content of malondialdehyde(MDA) were determined using colorimetric method to detect the oxidative stress in the liver of chickens. Blood biochemical indexes(ALT, AST and GGT), antioxidant indicators(SOD, GSH and MDA) in liver homogenates and pathologic changes in tissues were detected at 14 d, 28 d and 42 d respectively. The results indicated that the clinical symptoms and the pathological change were different when comparing the three Cr(VI)-treated groups with the control groups. The liver organ coefficients in the three Cr(VI)-treated groups showed significant differences compared to the control group with the increasing exposure time and concentrations, there is a obvious growth trend of organ coefficients. The levels of white blood cell(WBC) all increased significantly(P< 0.05) in three Cr(VI)-treated groups compared to the control group, however, the levels of red blood cell(RBC) and WBC decreased significantly(P< 0.05) in 28 days group and 42 days group. The blood biochemical indexes indicated that Aspartate Aminotransferase Ammonia(ALT) increased significantly(P< 0.05) in three Cr(VI)-treated groups compared to the control group. Nevertheless, both Alanine Aminotransferase(AST) and Glutamyl Endopeptidase(GGT) increased with the increasing doses; and in the high-dose group at 28 days and 42 days they showed significant differences(P< 0.05). According to pathological results, in the low-does group and the control group, the hepatocyte arranged relatively close, the hepatic cords were in order and the structure of lobular was normal. However, with the increasing concentrations of hexavalent chromium the cytoplasm became loose with vacuolar degeneration, granular degeneration and hepatic sinus gap expansion; and the cells in liver appeared necrosis, central venous became stenosis along with inflammatory cell infiltration in hepatocytes in middle-dose group and high-dose group. The activities of superoxide dismutase(SOD) and glutathione(GSH) increased significantly(P< 0.05) in three Cr(VI)-treated groups compared to the control group. However, the content of Malondialdehyde(MDA) decreased significantly(P< 0.05) than the control group as the increasing time and dose. The results indicated that Cr(VI) can lead to liver damage, antioxidant indicators irreversible damage in the liver and dysfunction in chicken.