Document Detail

The evolution of Root effect hemoglobins in the absence of intracellular pH protection of the red blood cell: insights from primitive fishes.
MedLine Citation:
PMID:  20213180     Owner:  NLM     Status:  MEDLINE    
The Root effect, a reduction in blood oxygen (O(2)) carrying capacity at low pH, is used by many fish species to maximize O(2) delivery to the eye and swimbladder. It is believed to have evolved in the basal actinopterygian lineage of fishes, species that lack the intracellular pH (pH(i)) protection mechanism of more derived species' red blood cells (i.e., adrenergically activated Na(+)/H(+) exchangers; betaNHE). These basal actinopterygians may consequently experience a reduction in blood O(2) carrying capacity, and thus O(2) uptake at the gills, during hypoxia- and exercise-induced generalized blood acidoses. We analyzed the hemoglobins (Hbs) of seven species within this group [American paddlefish (Polyodon spathula), white sturgeon (Acipenser transmontanus), spotted gar (Lepisosteus oculatus), alligator gar (Atractosteus spatula), bowfin (Amia calva), mooneye (Hiodon tergisus), and pirarucu (Arapaima gigas)] for their Root effect characteristics so as to test the hypothesis of the Root effect onset pH value being lower than those pH values expected during a generalized acidosis in vivo. Analysis of the haemolysates revealed that, although each of the seven species displayed Root effects (ranging from 7.3 to 40.5% desaturation of Hb with O(2), i.e., Hb O(2) desaturation), the Root effect onset pH values of all species are considerably lower (ranging from pH 5.94 to 7.04) than the maximum blood acidoses that would be expected following hypoxia or exercise (pH(i) 7.15-7.3). Thus, although these primitive fishes possess Hbs with large Root effects and lack any significant red blood cell betaNHE activity, it is unlikely that the possession of a Root effect would impair O(2) uptake at the gills following a generalized acidosis of the blood. As well, it was shown that both maximal Root effect and Root effect onset pH values increased significantly in bowfin over those of the more basal species, toward values of similar magnitude to those of most of the more derived teleosts studied to date. This is paralleled by the initial appearance of the choroid rete in bowfin, as well as a significant decrease in Hb buffer value and an increase in Bohr/Haldane effects, together suggesting bowfin as the most basal species capable of utilizing its Root effect to maximize O(2) delivery to the eye.
Matthew D Regan; Colin J Brauner
Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2010-03-06
Journal Detail:
Title:  Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology     Volume:  180     ISSN:  1432-136X     ISO Abbreviation:  J. Comp. Physiol. B, Biochem. Syst. Environ. Physiol.     Publication Date:  2010 Jun 
Date Detail:
Created Date:  2010-05-18     Completed Date:  2010-08-12     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  8413200     Medline TA:  J Comp Physiol B     Country:  Germany    
Other Details:
Languages:  eng     Pagination:  695-706     Citation Subset:  IM    
Department of Zoology, University of British Columbia, 6270 University Boulevard, Vancouver, BC, Canada.
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MeSH Terms
Erythrocytes / metabolism*
Evolution, Molecular
Fish Proteins / genetics,  physiology*
Fishes / blood*,  genetics
Hemoglobins / analysis,  genetics,  physiology*
Hydrogen-Ion Concentration
Oxygen / blood*
Reg. No./Substance:
0/Fish Proteins; 0/Hemoglobins; 7782-44-7/Oxygen

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