Vol. 274, Issue 3, R661-R671, March 1998
Carbon dioxide transport in alligator blood and its
erythrocyte permeability to anions and water
Frank B.
Jensen1,
Tobias
Wang1,
David R.
Jones2, and
Jesper
Brahm3
1 Institute of Biology, Odense
University, DK-5230 Odense M; 3 Department of
Medical Physiology, The Panum Institute, Copenhagen University, DK-2200
Copenhagen N, Denmark; and 2 Department of
Zoology, University of British Columbia, Vancouver, V6T 1Z4 Canada
Deoxygenation of alligator red blood cells (RBCs) caused binding
of two 
equivalents per hemoglobin (Hb) tetramer at physiological pH. At lowered pH, some
binding also occurred to
oxygenated Hb. The erythrocytic total CO2 content was large, and
Hb-bound , free , and carbamate contributed about
equally in deoxygenated cells. The nonbicarbonate buffer values of RBCs and Hb were high, and the Hb showed a significant fixed acid Haldane effect. Binding of on
deoxygenation occurred without a change in RBC intracellular pH,
revealing equivalence between oxylabile
and
H+ binding. Erythrocyte volume,
plasma pH, and plasma concentration also varied little with the degree of
oxygenation. Diffusional water permeability was higher in oxygenated
than deoxygenated RBCs. The RBCs have rapid band 3-mediated
Cl
and
transport, which was not affected by degree of oxygenation, but net fluxes of
Cl and
via the anion exchanger are small during blood circulation at rest. Most of the
CO2 taken up into the blood as it
flows through tissue capillaries is carried within the erythrocytes as
Hb-bound until
CO2 is excreted when blood flows
through pulmonary capillaries.
allosteric binding of bicarbonate; red cell anion exchange; Haldane
effect; blood CO2 transport; crocodiles
