Teleosts in hypoxia: Aspects of anaerobic metabolism

Van den Thillart, G. & van Waarde, A., 1985, In : Molecular physiology. 8, p. 393-409 17 p.

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Moderate hypoxia can be tolerated by many fish species, while only some species survive severe hypoxia or anoxia. Hypoxia usually activates anaerobic glycolysis, which may be temporary when the animals are able to improve their oxygen extraction capacity. Switching over to aerobic metabolism allows the animals to adapt to hypoxia. Under anoxic conditions survival appears to be restricted by (1) the capacity for anaerobic energy production, as well as by (2) the extent to which metabolic rate can be depressed. An extreme example for both aspects is provided by the hibernating crucian carp. The effect of anoxia on in vivo metabolic levels of a few species is discussed. It is evident that glycolysis and creatine phosphate breakdown are the major pathways for anaerobic energy production in fish. In goldfish and crucian carp, a modified glycolysis is found: lactate does not accumulate. Instead, pyruvate is decarboxylated in the muscle tissues to acetaldehyde, which is reduced in the cytoplasm by alcohol dehydrogenase. Since this mechanism is not coupled to energy conservation, the reaction is down-hill, further stimulated by the diffusion of CO2 and ethanol into the environment. The major advantage of this reaction lies presumably in the prevention of metabolic acidosis. Several experiments with anoxic goldfish demonstrated that there is in addition a significant Krebs' cycle activity. Particularly interesting is the anaerobic decarboxylation of glutamate by tissue homogenates and isolated mitochondria. Several lines of evidence indicate that protein catabolism is of quantitative importance during anaerobiosis; a few metabolic pathways are discussed.
Original languageEnglish
Pages (from-to)393-409
Number of pages17
JournalMolecular physiology
Publication statusPublished - 1985



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