Characteristics of the anion transport system in sea turtle erythrocytes

E. K. Stabenau, C. G. Vanoye, T. A. Heming*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

10 Scopus citations

Abstract

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 HCO3--Cl- exchange with 4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonic acid (SITS), sea turtle erythrocytes were found to contain 4 x 106 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 μM (10°C, pH 7.6). Under physiological conditions (30°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.

Original languageEnglish (US)
JournalAmerican Journal of Physiology - Regulatory Integrative and Comparative Physiology
Volume261
Issue number5 30-5
StatePublished - Dec 1 1991

Keywords

  • Anion exchange
  • Band 3
  • Erythrocyte
  • Lepidochelys
  • Reptile

ASJC Scopus subject areas

  • Physiology

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