Dioxide

Comp. Biochem. Physiol. Vol. 113A, No. 1, pp. 83-90,
Copynght 0 1996 Elsevier Science Inc.

ISSN 0300-9629/96/$15.00
SSDI 0300-9629(95)02062-4

1996

ELSEVIER

REVIEW

The Interaction Between Oxygen
and Carbon Dioxide Movements in Fishes
C. J. Bruuner and D. J. Randall
DEPARTMENT OF ZOOLOGY, UNIVERSITY OF BRITISH COLUMBIA, VANCOUVER, BRITISH COLUMBIA, CANADA, V6T

ABSTRACT. Manyteleost fishes have haemoglobins

a low buffer capacity.
oxygen and carbon

This combination

dioxide

which possess a Root effect,

of characteristics

in the red cell,

influences

in the respiratory

epithelium,

However,

muscle capillary

transit,

the Root effect is probably
enhancing

some teleost

dehydration

in maintaining

of haemoglobin-oxygensaturation

gills and in conserving

body CO2 stores during exposure

(27).

equilibrium

KEY WORDS. Bohr protons,

binding

facilitates

This trait is probably significant

Haldane

effect,

to hypoxia

fish, oxygen,

CO,

hydration

in maximizing

and exercise,

carbon dioxide,

ide (CO,) on the affinity of blood for 0, (Bohr effect) in
vertebrates. In 1914,Christiansen, Douglas and Haldane (11)
discovered that the CO2 content of deoxygenated blood was
greater than that of oxygenated blood (Haldane effect), implicating the role of haemoglobin (Hb) in both CO1 and 0,
transport. These studies, among others, sparked investigations
into the interaction between oxygen and carbon dioxide transport in the blood of vertebrates, which continues to thepresent, unabated. Most of these studies have been conducted in
For example, the
while the other is

held constant, while in viva, gas exchange at all levels involves
simultaneous changes in both 0, and CO,. Thus, although
the fact that an interaction exists between movements of 0,
and CO, is undisputed, the physiological importance of this
interaction remains largely unresolved, especiallyin lower vertebrates such as fish.

Models of gas transfer across the respiratory surface incorporate ventilation,
diffusion and perfusion limitations but selAddress reprint requests to: C. J. Brauner, Dept. of Zoology, Univ. of British
Columbia, Vancouver, British Columbia, Canada, V6T 124.
Received 17 January 1995; revised 28 April 1995; accepted 11 August
1995.

In

between

50 and100%

oxygen

uptake at the
of

1996.
hypoxia,

of oxygen

exercise

and carbon

dioxide in the

blood, even though such reactions are often considered to be
rate limiting (49). Most of the CO, excreted across the gills
is carried in the blood as bicarbonate (HCOj-)
which must
be dehydrated to CO, within the red cell (43). Conversely,
most of the 0, taken up from the water istransported away
from the gills bound to Hb. Thus, gas exchange must be
treated as an “overall equilibration conductance” (49), taking
into account the rates of gaseous diffusion and chemical reactions.
Because Hb-oxygenation
releases protons and HCO,dehydration consumes protons, there is an extensive interaction
between oxygen and carbon dioxide transfer. This interaction
occurs in theblood, centered on the red blood cell, in both
the tissues and the respiratory epithelium.

Acidification

of the

blood effects oxygen binding to Hb via the Bohr effect and
the Root shift, in many teleost fishes. The movement of oxylabile Bohr protons in the blood drives HCO,dehydration
in the respiratory epithelium
O2 TRANSPORT

IN FISH

facilitates

at the tissues.

when thelower reaches

interaction,

dom include reactions

The classic study by Bohr, Hasselbalch and Krogh in 1904
(Z), was the first to demonstrate the influence of carbon diox-

GAS EXCHANGE

upon

blood PO, during

curve are used. COMP BIOCHEM PHYSIOL 113A;1:83-90,

INTRODUCTION

vitro, under nonphysiological
conditions.
partial pressure of one gas is manipulated

of

released...