title: The absence of ion-regulatory suppression in the gills of the aquatic air-breathing fish Trichogaster lalius during oxygen stress.
abstract: The strategy for most teleost to survive in hypoxic or anoxic conditions is to conserve energy expenditure, which can be achieved by suppressing energy-consuming activities such as ion regulation. However, an air-breathing fish can cope with hypoxic stress using a similar adjustment or by enhancing gas exchange ability, both behaviorally and physiologically. This study examined Trichogaster lalius, an air-breathing fish without apparent gill modification, for their gill ion-regulatory abilities and glycogen utilization under a hypoxic treatment. We recorded air-breathing frequency, branchial morphology, and the expression of ion-regulatory proteins (Na(+)/K(+)-ATPase and vacuolar-type H(+)-ATPase) in the 1(st) and 4(th) gills and labyrinth organ (LO), and the expression of glycogen utilization (GP, glycogen phosphorylase protein expression and glycogen content) and other protein responses (catalase, CAT; carbonic anhydrase II, CAII; heat shock protein 70, HSP70; hypoxia-inducible factor-1α, HIF-1α; proliferating cell nuclear antigen, PCNA; superoxidase dismutase, SOD) in the gills of T. lalius after 3 days in hypoxic and restricted conditions. No morphological modification of the 1(st) and 4(th) gills was observed. The air-breathing behavior of the fish and CAII protein expression both increased under hypoxia. Ion-regulatory abilities were not suppressed in the hypoxic or restricted groups, but glycogen utilization was enhanced within the groups. The expression of HIF-1α, HSP70 and PCNA did not vary among the treatments. Regarding the antioxidant system, decreased CAT enzyme activity was observed among the groups. In conclusion, during hypoxic stress, T. lalius did not significantly reduce energy consumption but enhanced gas exchange ability and glycogen expenditure.
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.
authors.forename: Hsueh-Hsi
authors.initials: HH
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
authors.affiliation: Department of Life Science, Tunghai University, Taichung 40704, Taiwan; Center for Tropical Ecology and Biodiversity, Tunghai University, Taichung 40704, Taiwan.
authors.forename: Hui-Chen
authors.initials: HC
authors.lastname: Lin
mesh_terms: D000388:Air; D000818:Animals; D000975:Antioxidants / Q000378:metabolism; D059001:Aquatic Organisms / Q000378:metabolism*; D002256:Carbonic Anhydrases / Q000378:metabolism; D002374:Catalase / Q000378:metabolism; D005260:Female; D005786:Gene Expression Regulation; D005880:Gills / Q000378:metabolism*; D006003:Glycogen / Q000378:metabolism; D024981:Glycogen Phosphorylase / Q000235:genetics / Q000378:metabolism; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism; D000860:Hypoxia / Q000378:metabolism; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000235:genetics / Q000378:metabolism; D007477:Ions / Q000378:metabolism*; D008297:Male; D010100:Oxygen / Q000378:metabolism*; D010473:Perciformes / Q000097:blood / Q000378:metabolism*; D018809:Proliferating Cell Nuclear Antigen / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012119:Respiration; D012964:Sodium / Q000097:blood; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism; D013312:Stress, Physiological; D013482:Superoxide Dismutase / Q000378:metabolism; D013997:Time Factors; D025262:Vacuolar Proton-Translocating ATPases / Q000378:metabolism
chemical_list: D000975:Antioxidants; D018840:HSP70 Heat-Shock Proteins; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D007477:Ions; D018809:Proliferating Cell Nuclear Antigen; D012333:RNA, Messenger; D006003:Glycogen; D012964:Sodium; D002374:Catalase; D013482:Superoxide Dismutase; D024981:Glycogen Phosphorylase; D025262:Vacuolar Proton-Translocating ATPases; D002256:Carbonic Anhydrases; D000254:Sodium-Potassium-Exchanging ATPase; D010100:Oxygen
keywords: Air-breathing behavior; Antioxidant enzyme; Glycogen utilization; Hypoxia; Labyrinth organ; Na(+)/K(+)-ATPase