title: The combined effect of hypoxia and nutritional status on metabolic and ionoregulatory responses of common carp (Cyprinus carpio).
abstract: In the present study, the combined effects of hypoxia and nutritional status were examined in common carp (Cyprinus carpio), a relatively hypoxia tolerant cyprinid. Fish were either fed or fasted and were exposed to hypoxia (1.5-1.8mg O2L(-1)) at or slightly above their critical oxygen concentration during 1, 3 or 7days followed by a 7day recovery period. Ventilation initially increased during hypoxia, but fasted fish had lower ventilation frequencies than fed fish. In fed fish, ventilation returned to control levels during hypoxia, while in fasted fish recovery only occurred after reoxygenation. Due to this, C. carpio managed, at least in part, to maintain aerobic metabolism during hypoxia: muscle and plasma lactate levels remained relatively stable although they tended to be higher in fed fish (despite higher ventilation rates). However, during recovery, compensatory responses differed greatly between both feeding regimes: plasma lactate in fed fish increased with a simultaneous breakdown of liver glycogen indicating increased energy use, while fasted fish seemed to economize energy and recycle decreasing plasma lactate levels into increasing liver glycogen levels. Protein was used under both feeding regimes during hypoxia and subsequent recovery: protein levels reduced mainly in liver for fed fish and in muscle for fasted fish. Overall, nutritional status had a greater impact on energy reserves than the lack of oxygen with a lower hepatosomatic index and lower glycogen stores in fasted fish. Fasted fish transiently increased Na(+)/K(+)-ATPase activity under hypoxia, but in general ionoregulatory balance proved to be only slightly disturbed, showing that sufficient energy was left for ion regulation.
authors.affiliation: Systemic Physiological and Ecotoxicological Research, Department of Biology, University of Antwerp, Groenenborgerlaan 171, BE-2020 Antwerp, Belgium. Electronic address: Sofie.Moyson@uantwerpen.be.
authors.forename: Sofie
authors.initials: S
authors.lastname: Moyson
authors.affiliation: Systemic Physiological and Ecotoxicological Research, Department of Biology, University of Antwerp, Groenenborgerlaan 171, BE-2020 Antwerp, Belgium; Institute of Tropical Aquaculture, University Malaysia Terengganu, 21030 Kuala Terengganu, Terengganu, Malaysia.
authors.forename: Hon Jung
authors.initials: HJ
authors.lastname: Liew
authors.affiliation: Systemic Physiological and Ecotoxicological Research, Department of Biology, University of Antwerp, Groenenborgerlaan 171, BE-2020 Antwerp, Belgium.
authors.forename: Marjan
authors.initials: M
authors.lastname: Diricx
authors.affiliation: Systemic Physiological and Ecotoxicological Research, Department of Biology, University of Antwerp, Groenenborgerlaan 171, BE-2020 Antwerp, Belgium.
authors.forename: Amit Kumar
authors.initials: AK
authors.lastname: Sinha
authors.affiliation: Systemic Physiological and Ecotoxicological Research, Department of Biology, University of Antwerp, Groenenborgerlaan 171, BE-2020 Antwerp, Belgium.
authors.forename: Ronny
authors.initials: R
authors.lastname: Blust
authors.affiliation: Systemic Physiological and Ecotoxicological Research, Department of Biology, University of Antwerp, Groenenborgerlaan 171, BE-2020 Antwerp, Belgium.
authors.forename: Gudrun
authors.initials: G
authors.lastname: De Boeck
mesh_terms: D000641:Ammonia / Q000097:blood; D000818:Animals; D002347:Carps / Q000097:blood / Q000378:metabolism*; D004734:Energy Metabolism / Q000502:physiology; D005215:Fasting / Q000097:blood; D005247:Feeding Behavior; D005880:Gills / Q000201:enzymology; D006003:Glycogen / Q000378:metabolism; D000860:Hypoxia / Q000378:metabolism*; D007477:Ions / Q000097:blood; D019344:Lactic Acid / Q000097:blood; D050356:Lipid Metabolism; D008099:Liver / Q000378:metabolism; D009132:Muscles / Q000378:metabolism; D009752:Nutritional Status; D011506:Proteins / Q000378:metabolism; D012119:Respiration; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism
chemical_list: D007477:Ions; D011506:Proteins; D019344:Lactic Acid; D000641:Ammonia; D006003:Glycogen; D000254:Sodium-Potassium-Exchanging ATPase
keywords: Fasting; Na(+)/K(+)-ATPase activity; Normoxic recovery; Ventilation frequency