| Polycyclic aromatic hydrocarbon (PAHs) pollution has become seriously and attracted much attention all over the world due to the development of maritime petroleum, marine traffic and industry sewerage discharge. PAHs are known as teratogens, carcinogens and mutagens, and 16 kinds of PAHs are on the United States Environmental Protection Agency's priority pollutant list. Anthracene (ANT) is the simplest liner triaromatics and the parent structure of the other complicated PAHs and exists widely in natural water. It has the strongest phototoxicity and fastest photo modified reaction rate. Studying the physiological and biochemical effects of ANT on the marine organism would provide basic experimental evidences for further studies about complex PAHs.The present study is conducted to evaluate the potentially toxic effects of ANT on marine sentinental organisms and find out the possible early-warning biomarker(s). Mytius galloprpvincialis is chosen as the target organism and the main research contents include:studying the physiological and biochemical effects of low-concentration and long-time sublethal stress of ANT in the different tissues of the mussels (gills and digestive glands);researched the difference in sensitivity to antioxidant responses in both tissues; discussed the possible mechanism preliminarily, in order to screen out the representative and high-sensitive biomarker(s) which can reflect the ANT pollution status in Jiaozhou Bay offshore. Results show that:1 The effects of sublethal stress of ANT on growth of M. galloprpvincialisThe influences of the concentrations of ANT on the shell length and dry weight of the mussels have been studied. And the results show that a long time (21 days) sublethal stress of ANT can not basically affect the growth of the mussels compared with control group (P>0.05). 2 The effects of sublethal stress of ANT on antioxidant defense system of M. galloprpvincialisGlutathione plays an important role in the metabolic process of organic copunds in organisms, since the changes of enzymy activity related to the GSH are determined systematically. Results show that:(1)Glutathione S-Transferase (GST)In mussels' gills, no significant changes in GST activity are found under long-time ANT stress compared with control group (P>0.05). In mussels' digestive glands, ANT concerntration 0.25μg/L (the experimental group of low concentration in ANT) can induce the increased activity of GST significantly (P<0.05); no significant changes in GST activity are found under ANT concerntration 2.5μg/L (the experimental group of high concentration in ANT) (P>0.05).(2)Glutathione Peroxidase (GPx)In mussels'gills, low-concentration ANT stress can induce the activity of GPx increased significantly (P<0.05), and no significant changes in GPx activity are found under high-concentration ANT stress (P>0.05). In mussels' digestive glands, the changes of GPx activity are different in mussels' gills, and GPx activity can be induced significantly all of experimental group compared with control group (P<0.05).(3)Glutathione Reductase (GR):In mussels' gills, no significant changes in GR activity are found under long-time ANT stress (P>0.05). In mussels' digestive glands, no significant changes in GR activity are found under low-concentration ANT stress (P>0.05), but high-concentration ANT stress can induce the activity of GR increased significantly (P<0.05).(4)Glutathione (GSH)In mussels' gills, low-concentration ANT stress can inhibit histocytes to generate GSH (P<0.05), but high-concentration ANT stress can induce histocytes to generate GSH (P<0.05), significantly. In mussels'digestive glands, the concents of GSH are induced significantly in the whole experimental process (P<0.05).3 The effects of sublethal stress of ANT on malondialdehyde (MDA) and surperoxide anion radical (O2-·) contents in M. galloprpvincialisIn mussels' gills low-concentration ANT stress can induce histocytes to generate MDA significantly, and the differences are obviously compared with control group (P<0.05), but high-concentration ANT stress can hardly affect the contents of MDA compared with control group in the whole experimental process (P>0.05). In mussels' digestive glands no significant changes in MDA content are found under ANT stress (P>0.05). At the same time, the detection results of O2-·contents show that:In mussels' gills, low-concentration ANT stress can induce the productions of O2-·significantly and lead to O2-·contents increased (P<0.05), but high-concentration ANT stress can hardly affect the changes of O2-·contents compared with control group (P>0.05). In mussels' digestive glands, the changes of O2-·contents are different from mussels' gills, and ANT stress can induce the productions of O2-·significantly and lead to O2-·contents increased compared with control group (P<0.05).4 Preliminary studying on the mechanism of the effects of ANT stress on M. galloprpvincialisResults show that:To a certain extent, ANT stress is related to oxidative stress and antioxidant defense system. ANT stress lead to the changes of MDA and O2-·contents in both tissues of mussels.There are some correlations between MDA and O2-·contents. In the later stage of the experiment (after 18 days), significant correlations are found between MDA and O2-·contents (P<0.05). Further analysis results show that:MDA contents have a remarkable correlation with GR activities (P<0.05), and O2-·contents have very significantly correlation with GST, GPx and GR activities (P<0.01).In a word, ANT stress results in the degree of lipid peroxidation increased, the levels of reactive oxygene species increased and the oxidative stress generated, obviously. The antioxidant enzymes including GST, GPx and GR play an important role in the clearence of radicals and the remission of oxidative stress. Meanwhile, the results show that the mussels'digestive gland is more sensitive under long-time sublethal stress of ANT, and it is the primary target organ. GPx activities, GSH and O2-·contents are very sensitive to the responses of ANT stress and can be used as the high-sensitive biomarkers for ANT stress. |
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