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Cod (Gadus morhua) Cardiorespiratory Physiology and Hypoxia Tolerance following Acclimation to Low-Oxygen Conditions.
MedLine Citation:
PMID:  21050128     Owner:  NLM     Status:  In-Data-Review    
Abstract/OtherAbstract:
Abstract Previous research has shown that hypoxia-acclimated Atlantic cod (Gadus morhua) have significantly reduced cardiac function but can consume more oxygen for a given cardiac output (Q). However, it is not known (1) which physiological changes permit a greater "oxygen pulse" (oxygen consumed per mL of blood pumped) in hypoxia-acclimated individuals or (2) whether chronic exposure to low-oxygen conditions improves the hypoxia tolerance of cod. Thus, we exposed normoxia- and hypoxia-acclimated (>6 wk at a water oxygen partial pressure [P(w)o(2)] of ∼8-9 kPa) cod to a graded normoxia challenge until loss of equilibrium occurred while recording the following cardiorespiratory variables: oxygen consumption (Mo(2)), ventilatory rate, cardiac function (Q, heart rate f(H), and stroke volume S(V)), ventral aortic blood pressure (P(VA)), venous oxygen partial pressure (P(v)o(2)) and oxygen content (C(v)o(2)), plasma catecholamines, and blood hemoglobin ([Hb]) and hematocrit (Hct). In addition, we performed in vitro hemoglobin oxygen binding curves to examine whether hypoxia acclimation influences hemoglobin functional properties. Numerous physiological adjustments occurred in vivo during the >6 wk of hypoxia acclimation: that is, increased f(H), decreased S(V) and Q, elevated [Hb], enhanced tissue oxygen extraction (by 10% at a P(w)o(2) of 20 kPa), and a more robust stress response as evidenced by circulating catecholamine levels that were two to eight times higher when fish were acutely exposed to severe hypoxia. In contrast, chronic hypoxia had no significant effect on the affinity of hemoglobin for oxygen, on in vitro hemoglobin oxygen carrying capacity, or on the cod's hypoxia tolerance (H(crit); the P(w)o(2) at which the fish lost equilibrium, which was 4.3 ± 0.2 and 4.8 ± 0.3 kPa in normoxia- and hypoxia-acclimated fish, respectively). These data suggest that while chronic hypoxia results in numerous physiological adjustments, these changes do not improve the cod's capacity to tolerate low-oxygen conditions.
Authors:
L H Petersen; A Kurt Gamperl
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Physiological and biochemical zoology : PBZ     Volume:  84     ISSN:  1537-5293     ISO Abbreviation:  Physiol. Biochem. Zool.     Publication Date:    2011 Jan-Feb
Date Detail:
Created Date:  2011-04-04     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  100883369     Medline TA:  Physiol Biochem Zool     Country:  United States    
Other Details:
Languages:  eng     Pagination:  18-31     Citation Subset:  IM    
Affiliation:
Ocean Sciences Centre, Memorial University of Newfoundland, St. John's, A1C 5S7 Newfoundland, Canada.
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