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Am J Physiol Regul Integr Comp Physiol 261: R1218-R1225, 1991;
0363-6119/91 $5.00
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AJP - Regulatory, Integrative and Comparative Physiology, Vol 261, Issue 5 1218-R1225, Copyright © 1991 by American Physiological Society

ARTICLES

Characteristics of the anion transport system in sea turtle erythrocytes

E. K. Stabenau, C. G. Vanoye and T. A. Heming
Pulmonary Research Laboratories, University of Texas Medical Branch, Galveston 77550.

Erythrocytes of Kemp's ridley sea turtle (Lepidochelys kempi) contain a 100- to 105-kDa protein that is reactive with a monoclonal antibody to the membrane domain of human erythrocyte band 3. Based on inhibition of membrane HCO(3-)-Cl- exchange with 4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonic acid (SITS), sea turtle erythrocytes were found to contain 4 x 10(6) copies of band 3 per cell. Unidirectional HCO3- transfer, specifically HCO3- out----in-Cl-in----out exchange, where subscript in----out represents transfer from inside to outside and subscript out----in represents transfer from outside to inside, was characterized by a maximal exchange rate of 1.0-1.1 nmol.cm-2.s-1, substrate affinity coefficients of 0.1-0.2 mM for HCO3- and 1.6 mM for Cl-, and an apparent inhibition constant for SITS of 0.6-1.0 microM (10 degrees C, pH 7.6). Under physiological conditions (30 degrees C, pH 7.4), the rate of net HCO3- transfer (i.e., the difference between HCO3- in----out-Cl-out----in and HCO3- out----in-Cl-in----out) was 1.13 nmol. cm-2.s-1 for cells subjected to a 5-mM decrement in CO2 content. This yields a rate coefficient for the "physiological" anion shift in sea turtle blood of 1.7 s-1, indicating that the anion shift may require 2.6 s to reach 99% completion in vivo. The erythrocyte anion shift appears to be a potential rate-limiting step for capillary CO2 exchange in these turtles.


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Carbon dioxide transport in alligator blood and its erythrocyte permeability to anions and water
Am J Physiol Regulatory Integrative Comp Physiol, March 1, 1998; 274(3): R661 - R671.
[Abstract] [Full Text] [PDF]


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