title: Effects of hypoxia on ionic regulation, glycogen utilization and antioxidative ability in the gills and liver of the aquatic air-breathing fish Trichogaster microlepis.
abstract: We examined the hypothesis that Trichogaster microlepis, a fish with an accessory air-breathing organ, uses a compensatory strategy involving changes in both behavior and protein levels to enhance its gas exchange ability. This compensatory strategy enables the gill ion-regulatory metabolism to maintain homeostasis during exposure to hypoxia. The present study aimed to determine whether ionic regulation, glycogen utilization and antioxidant activity differ in terms of expression under hypoxic stresses; fish were sampled after being subjected to 3 or 12h of hypoxia and 12h of recovery under normoxia. The air-breathing behavior of the fish increased under hypoxia. No morphological modification of the gills was observed. The expression of carbonic anhydrase II did not vary among the treatments. The Na(+)/K(+)-ATPase enzyme activity did not decrease, but increases in Na(+)/K(+)-ATPase protein expression and ionocyte levels were observed. The glycogen utilization increased under hypoxia as measured by glycogen phosphorylase protein expression and blood glucose level, whereas the glycogen content decreased. The enzyme activity of several components of the antioxidant system in the gills, including catalase, glutathione peroxidase, and superoxidase dismutase, increased in enzyme activity. Based on the above data, we concluded that T. microlepis is a hypoxia-tolerant species that does not exhibit ion-regulatory suppression but uses glycogen to maintain energy utilization in the gills under hypoxic stress. Components of the antioxidant system showed increased expression under the applied experimental treatments.
authors.affiliation: Department of Life Science, Tunghai University, Taichung 40704, Taiwan; Department of Chemistry, National Taiwan Normal University, Taipei 11677, Taiwan.
authors.forename: Chun-Yen
authors.initials: CY
authors.lastname: Huang
authors.affiliation: Department of Life Science, Tunghai University, Taichung 40704, Taiwan; Center for Tropical Ecology and Biodiversity, Tunghai University, Taichung 40704, Taiwan. Electronic address: hclin@thu.edu.tw.
authors.forename: Hui-Chen
authors.initials: HC
authors.lastname: Lin
authors.affiliation: Department of Chemistry, National Taiwan Normal University, Taipei 11677, Taiwan.
authors.forename: Cheng-Huang
authors.initials: CH
authors.lastname: Lin
mesh_terms: D000388:Air; D000825:Animal Structures / Q000378:metabolism; D000818:Animals; D000975:Antioxidants / Q000378:metabolism*; D059001:Aquatic Organisms / Q000378:metabolism; D001786:Blood Glucose / Q000378:metabolism; D002256:Carbonic Anhydrases / Q000235:genetics / Q000378:metabolism; D002374:Catalase / Q000378:metabolism; D005260:Female; D005786:Gene Expression Regulation; D005880:Gills / Q000378:metabolism*; D005979:Glutathione Peroxidase / Q000378:metabolism; D006003:Glycogen / Q000378:metabolism*; D024981:Glycogen Phosphorylase / Q000378:metabolism; D000860:Hypoxia / Q000378:metabolism*; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000235:genetics / Q000378:metabolism; D007477:Ions / Q000378:metabolism; D008099:Liver / Q000378:metabolism*; D008297:Male; D010473:Perciformes / Q000033:anatomy & histology / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012119:Respiration; D000254:Sodium-Potassium-Exchanging ATPase / Q000235:genetics / Q000378:metabolism; D013482:Superoxide Dismutase / Q000378:metabolism
chemical_list: D000975:Antioxidants; D001786:Blood Glucose; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D007477:Ions; D012333:RNA, Messenger; D006003:Glycogen; D002374:Catalase; D005979:Glutathione Peroxidase; D013482:Superoxide Dismutase; D024981:Glycogen Phosphorylase; D002256:Carbonic Anhydrases; D000254:Sodium-Potassium-Exchanging ATPase
keywords: Air-breathing behavior; Antioxidant enzyme; Glucose; Labyrinth organ; Morphology; PAS-stain