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First published online May 21, 2007
Journal of Experimental Biology 210, 1935-1943 (2007)
Published by The Company of Biologists 2007
doi: 10.1242/jeb.005371
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Responses to hypoxia and recovery: repayment of oxygen debt is not associated with compensatory protein synthesis in the Amazonian cichlid, Astronotus ocellatus

J. M. Lewis1,*, I. Costa1, A. L. Val2, V. M. F. Almeida-Val2, A. K. Gamperl1 and W. R. Driedzic1

1 Ocean Sciences Centre, Memorial University of Newfoundland, St. John's, NL, A1C 5S7, Canada
2 Laboratory of Ecophysiology and Molecular Evolution, Instituto Nacional de Pesquisas da Amazônia, Alameda Cosme Ferreira, 1756, 69.083-000, Manaus, Amazonas, Brazil

* Author for correspondence (e-mail: jmlewis{at}mun.ca)

Accepted 5 March 2007

Oxygen consumption, as an indicator of routine metabolic rate (RoMR), and tissue-specific changes in protein synthesis, as measured by 3H-labelled phenylalanine incorporation rates, were determined in Astronotus ocellatus to investigate the cellular mechanisms behind hypoxia-induced metabolic depression and recovery. RoMR was significantly depressed, by approximately 50%, when dissolved oxygen levels reached 10% saturation (0.67±0.01 mg l–1 at 28±1°C). This depression in RoMR was accompanied by a 50–60% decrease in liver, heart and gill protein synthesis, but only a 30% decrease in brain protein synthesis. During recovery from hypoxia, an overshoot in RoMR to 270% of the normoxic rate was observed, indicating the accumulation of an oxygen debt during hypoxia. This conclusion was consistent with significant increase in plasma lactate levels during the hypoxic exposure, and the fact that lactate levels rapidly returned to pre-hypoxic levels. In contrast, a hyperactivation of protein synthesis did not occur, suggesting the overshoot in oxygen consumption during recovery is attributed to an increase in cellular processes other than protein synthesis.

Key words: hypoxia, recovery, routine metabolic rate, protein synthesis, lactate production, Astronotus ocellatus






© The Company of Biologists Ltd 2007