- Library Home /
- Search Collections /
- Open Collections /
- Browse Collections /
- UBC Theses and Dissertations /
- The evolution of proton-triggered oxygen pumps : root...
Open Collections
UBC Theses and Dissertations
UBC Theses and Dissertations
The evolution of proton-triggered oxygen pumps : root effect haemogobins in basal actinopterygian fishes Regan, Matthew D.
Abstract
It has recently been proposed that the Root effect (reduction of blood oxygen carrying capacity at low pH) evolved in the basal actinopterygian lineage of fishes in the absence of red blood cell (RBC)pH1-protecting βNHE activity. Consequently, there is the potential for these species to experience a reduction in blood 0₂ carrying capacity, and thus 0₂ uptake at the gills, during a generalized acidosis associated with exercise, hypoxia, and hypercarbia. I analyzed the haemoglobins (Hbs) of seven species within the basal actinopterygian lineage (from basal to derived: 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)) based on the hypothesis that RBC pH1 is not reduced to low enough levels in the general circulation to activate their Root effects. This may result from either RBC buffering by Rb, or onset pH values of the Root effect that are lower than those produced by these generalized acidoses. The former was investigated via Hb titrations, which simultaneously assessed intrinsic Hb buffer capacities and oxylabile Haldane effects, while the latter was investigated by spectrophotemetric analyses of Hb 0₂ saturation over a pH spectrum of pH 5.5 to 8.5. The results suggest that the Rb proton-binding properties of these species’ Hbs unlikely play a major role in the buffering of the intracellular compartment of the RBC when compared with those Hb proton-binding properties of Root effect species with βNHE. However, the onset pH values of these seven species’ variably-sized Root effects were considerably lower than those expected to be produced by a hypoxia- or exercise-induced generalized acidosis. There was also a correlation between the presence of countercurrent choroid retia and low Hb buffer values, large Bohr/Haldane effects, large Root effects, and high Root effect onset pH values, which collectively suggest a different process of Root effect evolution than is currently assumed. Taken together, it appears as though 0₂ uptake is not jeopardized in these early Root effect species, despite their relatively low Hb proton binding properties and lack of βNHE.
Item Metadata
Title |
The evolution of proton-triggered oxygen pumps : root effect haemogobins in basal actinopterygian fishes
|
Creator | |
Publisher |
University of British Columbia
|
Date Issued |
2008
|
Description |
It has recently been proposed that the Root effect (reduction of blood oxygen
carrying capacity at low pH) evolved in the basal actinopterygian lineage of fishes in the
absence of red blood cell (RBC)pH1-protecting βNHE activity. Consequently, there is
the potential for these species to experience a reduction in blood 0₂ carrying capacity,
and thus 0₂ uptake at the gills, during a generalized acidosis associated with exercise,
hypoxia, and hypercarbia. I analyzed the haemoglobins (Hbs) of seven species within the
basal actinopterygian lineage (from basal to derived: 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)) based on the hypothesis that RBC pH1 is not reduced to
low enough levels in the general circulation to activate their Root effects. This may
result from either RBC buffering by Rb, or onset pH values of the Root effect that are
lower than those produced by these generalized acidoses. The former was investigated
via Hb titrations, which simultaneously assessed intrinsic Hb buffer capacities and
oxylabile Haldane effects, while the latter was investigated by spectrophotemetric
analyses of Hb 0₂ saturation over a pH spectrum of pH 5.5 to 8.5. The results suggest
that the Rb proton-binding properties of these species’ Hbs unlikely play a major role in
the buffering of the intracellular compartment of the RBC when compared with those Hb
proton-binding properties of Root effect species with βNHE. However, the onset pH
values of these seven species’ variably-sized Root effects were considerably lower than
those expected to be produced by a hypoxia- or exercise-induced generalized acidosis.
There was also a correlation between the presence of countercurrent choroid retia and low Hb buffer values, large Bohr/Haldane effects, large Root effects, and high Root
effect onset pH values, which collectively suggest a different process of Root effect
evolution than is currently assumed. Taken together, it appears as though 0₂ uptake is
not jeopardized in these early Root effect species, despite their relatively low Hb proton
binding properties and lack of βNHE.
|
Extent |
1855043 bytes
|
Genre | |
Type | |
File Format |
application/pdf
|
Language |
eng
|
Date Available |
2009-04-27
|
Provider |
Vancouver : University of British Columbia Library
|
Rights |
Attribution-NonCommercial-NoDerivatives 4.0 International
|
DOI |
10.14288/1.0067200
|
URI | |
Degree | |
Program | |
Affiliation | |
Degree Grantor |
University of British Columbia
|
Graduation Date |
2009-05
|
Campus | |
Scholarly Level |
Graduate
|
Rights URI | |
Aggregated Source Repository |
DSpace
|
Item Media
Item Citations and Data
Rights
Attribution-NonCommercial-NoDerivatives 4.0 International