| Summary: | 碩士 === 東海大學 === 生命科學系 === 101 === Recently, the rising in water temperature and the eutrophication caused by global warming, and anthropogenic discharge of the nitrogenous wastes, lead to a decrease in aquatic oxygen solubility. Serious consequences for aquatic life could be expected if the hypoxic condition prolongs for a period of time. To balance the O2 and metabolism demands, organisms may change from aerobic to anaerobic respiration by utilizing glycogen as the emergency fuel in glycogenolysis, and the function of sodium-potassium adenosine triphosphatase (Na+/K+-ATPase, NKA) may be depressed to preserve energy consumption. In the process of glycogenolysis, glycogen phosphorylase (GP) degrades glycogen in muscle and liver into glucose-1-phosphate for glycolysis. According to previous studies, the glycogen-rich cells (GR cells) in fish gills located right next to mitochondria-rich cells (MR cells). The degrading of glycogen in GR cells could, therefore, cope with high ATP demand from NKA in MR cells when fish is under stress. In addition to the metabolic suppression, organisms produce free radicals harmful to cells in the hypoxic and recovery conditions. Therefore, how organisms adapt to hypoxia is an important issue for survival. The aquatic air-breathing anabantoid fish Helostoma temminckii, with the accessory air-breathing organ labyrinth organ connected with the gills, can live in the hypoxic environment. From the previous studies, it is known that no inhibition of NKA protein abundance and activity in hypoxia was observed within the first three days of the experiment in the other air-breathing fish Trichogaster lalius which has similar gill morphology with H. temminckii. In the present study, it is hypothesized that GP in GR cells degrades glycogen to generate ATP so that NKA in the gills of H. temminckii will not be inhibited. H. temminckii has better antioxidant ability and this will help to prevent from free radical damages in hypoxia and recovery in normoxia. The result indicates that the aquatic air-breathing H. temminckii increased the air-breathing frequency under hypoxia. The protein abundance of GP increased during hypoxic treatment, but expression of NKA did not change accordingly. Glycogen contents degraded during hypoxic condition in the gills and liver. For the antioxidant mechanism in the gills, the superoxide dismutase (SOD) activity in recovery group was higher than that in the hypoxic group and the glutathione peroxidase (GPx) increased under hypoxic and recovery groups. Moreover, glutathione-s-transferase (GST) activity increased in the recovery group. In the liver, the SOD increased under hypoxia and, catalase (CAT) activity in recovery group was higher than that in the hypoxic group. Furthermore, glutathione reductase (GSR) activity increased in the recovery group. In conclusion, H. temminckii regulates its behavioral, biochemical and physiological conditions for surviving under stress condition.
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