| To investigate the defense function of glutathione system against the oxidative damage caused by cadmium (Cd) in Anodonta woodiana woodiana, the experiments were set up in six treatment groups (0,4.22,8.43,16.86,33.72 and 67.45 mg·L-1 of Cd) according to the LC50 of Cd within 96h (134.9mg·L-1).Then, the animals were treated with Cd for 24,48,72 and 96 hour respectively. The determinations of the contents of hydrogen peroxide (H2O2), the abilities to resist the ultra oxygen anion (O2·-), the inhibition of hydroxyl free radical (OH), the contents of reduced glutathione (GSH), the contents of oxidized glutathione(GSSG), the specific value of GSH and GSSG levels, the activities and total antioxidant capacities of glutathione S-transferase (GST) and glutathione reductase (GR) in mantle, gill, and liver. The results shown that:Firstly, compared with control group, the overall contents of H2O2 in the mantle, gill and liver of Anodonta woodiana woodiana elevated significantly and extremely significant (P<0.05, P<0.01).With the increase of concentration and the treated time of cadmium ion, the abilities of inhibiting hydroxyl free radical in mantle and liver has no obvious change. The abilities of inhibiting hydroxyl free radical in gills shows a significant or extremely remarkable decrease (P< 0.05, P< 0.01); Compared with control group, the resistant abilities of ultra oxygen anion in the three organ demonstrated a declining trend, and its have significant or extremely remarkable differences (P< 0.05, P< 0.01).Secondly, compared with control group, except for the significantly higher (P<0.05) of the contents of GSSG in the treatment group of 48 h,4.22 mg·L-1 in the gills, the the contents of GSH and GSSG in mantle and gills dropped significantly or extremely significantly(P<0.05, P<0.01); the ratio of GSH/GSSG in mantle has no obvious change (P> 0.05). The ratio of GSH/GSSG showed a decreasing trend at the low concentrations within 24,48,72,96h, while it showed a rising trend at high concentration; With the extension of time, the ratio of GSH/GSSG in the gills dropped at first and then showed a growth in low concentration (4.22,8.43 mg·L-1), while it demonstrated a gradual decline at high concentrations (33.72,67.45mg·L-1) and showed a significant difference compared with the control group (P< 0.05); the contents of GSH and the ratio of GSH/GSSG in the liver decreased significantly or extremely significantly (P< 0.05, P< 0.01), while the contents of GSSG has no significant difference compared with control group.Thirdly, the activities of GST in the gill showed a gradient decline (P< 0.01) within 24 h; In 48,72 and 96 h, the activities of GST increased in the whole, and grew in the low concentration while dropped in the high concentration, which showed a significant or extremely significant difference (P< 0.05, P< 0.01); the activities of GR in the gill increased significantly in 48 h,8.43mg·L-1, and 67.45mg·L-1196 h,4.22 mg·L-1; the activity of GST showed a overall trend of increase and have extremely significant differences (P< 0.01); the activity of GST reached at the highest in the processing group of 24 h,4.22 mg·L-1, and with the increase of concentration of cadmium, the activity of GST in the liver reduced gradually; the activity of GR in the liver showed a trend of increase as a whole and had significant or extremely significant difference (P<0.05, P< 0.01);With the extension of elevated concentration of Cd2+and exposure time, mantle’s T-AOC showed a increase at the low concentration, while maintain stability in the high concentration; Gill’s T-AOC appeared mainly as "activated"; Digestive gland’s T-AOC soared in a short time, and show the obvious relationship between time,dose and effect, and then, with the extension of time, the T-AOC increased firstly and showed a decrease at the end, which has a significant or extremely remarkable difference compared with the control group.Conclusions:First, the contents of H2O2, and the ability of inhibiting the ultra oxygen anion can reflect sensitively of the oxidative damage effect of the cadmium clam to the Anodonta woodiana woodiana; if the capacity of inhibiting hydroxyl free radicals in the gill reduced, it may be associated with the gill which bear the respiration of mussel body; The liver as a detoxifying organs, it can resist some oxidative damage of cadmium.Second, the change of the contents of GSH lead to the damage of cadmium, which were responsive and played an important role; the content of GSH and liver can be used as biochemical indexes of environmental monitoring and target organs respectively.Third, the GST detoxification enzymes is responsive to the cadmium toxicity, and liver response more quickly then the gill; the total antioxidant capacity strength of three organs successively is:the liver>the gill>the mantle.This study will provide the further theoretical foundation of proving the oxidative damage mechanism of bivalves induced by cadmium, in the meantime, it provides the basic data and technical support to the biological monitoring of cadmium pollution of water. |
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