Document Detail

Respiratory responses to progressive hypoxia in the Amazonian oscar, Astronotus ocellatus.
MedLine Citation:
PMID:  18555751     Owner:  NLM     Status:  MEDLINE    
This study determined the respiratory responses to progressive hypoxia in oscar, an extremely hypoxia-tolerant Amazonian cichlid. Oscar depressed oxygen consumption rates (MO2), beginning at a critical O2 tension (Pcrit) of 46Torr, to only 14% of normoxic rates at 10Torr. Total ventilation (Vw) increased up to 4-fold, entirely due to a rise in ventilatory stroke volume (no change in ventilatory frequency), and water convection requirement (Vw/MO2) increased substantially (up to 15-fold). Gill O2 extraction fell steadily, from 60% down to 40%. Although O2 transfer factor (an index of gill O2 diffusion capacity) increased transiently in moderate hypoxia, it decreased at 10Torr, which may have caused the increased expired-arterial PO2 difference. Venous PO2 was always very low (< or =7Torr). Anaerobic metabolism made a significant contribution to ATP supply, indicated by a 3-fold increase in plasma lactate that resulted in an uncompensated metabolic acidosis. Respiration of isolated gill cells was not inhibited until below 5Torr; because gill water PO2 always exceeded this value, hypoxic ion flux arrest in oscars [Wood et al., Am. J. Physiol. Reg. Integr. Comp. Physiol. 292, R2048-R2058, 2007] is probably not caused by O2 limitation in ionocytes. We conclude that metabolic depression and tolerance of anaerobic bi-products, rather than a superior capacity for O2 supply, allow oscar to thrive in extreme hypoxia in the Amazon.
Graham R Scott; Chris M Wood; Katherine A Sloman; Fathima I Iftikar; Gudrun De Boeck; Vera M F Almeida-Val; Adalberto L Val
Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2008-05-08
Journal Detail:
Title:  Respiratory physiology & neurobiology     Volume:  162     ISSN:  1569-9048     ISO Abbreviation:  Respir Physiol Neurobiol     Publication Date:  2008 Jul 
Date Detail:
Created Date:  2008-07-22     Completed Date:  2008-10-21     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  101140022     Medline TA:  Respir Physiol Neurobiol     Country:  Netherlands    
Other Details:
Languages:  eng     Pagination:  109-16     Citation Subset:  IM    
Department of Zoology, University of British Columbia, Vancouver V6T 1Z4, Canada.
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MeSH Terms
Adaptation, Physiological
Anaerobic Threshold / physiology*
Anoxia / metabolism*
Cell Respiration / physiology
Cichlids / physiology*
Energy Metabolism / physiology
Gills / cytology,  physiology
Lactic Acid / blood
Oxygen Consumption / physiology*
Respiratory Mechanics / physiology*
Reg. No./Substance:
50-21-5/Lactic Acid

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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