| Chromium element was considered to be one of the important chemical raw material and it played a huge role in the printing and dyeing, leather making and metallurgy industry.After the trivalent chromium Cr(III) was confirmed to be an important active ingredient of GTF, more and more attention would be paid to it in poultry feed industry. However, with the wide application of chromium, chromium accumulation toxicity occurred. Recently,several reports indicated that exposure to trivalent chromium for long time could induce body damage after chromium poisoning, while its damage mechanism was not clear.Although extensive studies have been carried out on trivalent chromium in many organs,few investigations have been conducted the biochemical indexes and pathological changes of the brain tissue. Therefore, in this study, different concentrations of trivalent chromium were added into drinking water to research the toxicity of trivalent chromium in the brain of chickens.This experiment was conducted to investigate the oxidative stress in chickens exposed to different concentrations of chromium trichloride(Cr Cl3) in drinking water. Seventy-two Hylan Brown male chickens were randomly divided into four groups: three experimental groups and one control group. The experimental groups were exposed to three different doses(50% LD50, 25% LD50, and 12.5% LD50) of Cr Cl3 mg/kg body weight for 42 days,while the control group was given the equivalent water. Every six chickens were slaughtered respectively at 14 d, 28 d, and 42 d. Brain tissues were removed and frozen in liquid nitrogen. The content of Cr in chicken was detect by flame atomic absorption spectroscopy. The activities of antioxidant enzymes(superoxide dismutase, catalase and glutathione peroxidase) and non-enzymatic index(glutathione, total antioxidant capacity,malondialdehyde, and hydrogen peroxide) were measured after obtaining the brain samplesto detect the oxidative stress in the brain of chickens. Small sections of the cerebrum were freshly prepared and fixed in 10% neutral-buffered formaldehyde for at least 24 h, and the histological section was made to detect the degree of brain tissue damage.Results suggested that the chicken's median lethal dose(LD50) of potassium dichromate was calculated by the method of Horn(LD50=5000 mg/kg body weight). After the chickens were exposed to Cr Cl3 for 14, 28 or 42 days, the content of Cr were higher(P< 0.05) compared with the control group in the brain, and 50% LD50 Cr(III) significantly increased(P < 0.05) the contents of malondialdehyde and hydrogen peroxide. The antioxidant enzyme activities, total glutathione concentration, and total antioxidant capacity decreased significantly(P < 0.05) compared with the controls and were consistent with the increase in dosage and time. Additionally, extensive histological alterations were observed in the chicken brain, and cytoplasmic vacuolation of neurons and nuclear condensation were discovered at 42 d, which resulted in the neuronal necrosis. However, chicken brain of control group were normal showed a uniform light purple or purple, complete capsule,clear boundaries. The chicken brain in three different groups(low-dose group, middle-dose group, high-dose group) showed different degrees of neuronal necrosis,and the damage was more obvious with the higher concentration of chromium chloride. Morever,oversleeve phenonmenon was found in middle-dose group.These results indicated that exposure to high-dose Cr Cl3 for certain time could induce the occurrence of oxidative stress and histological alterations. |
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