The conversion of plasma HCO3- to CO2 by rainbow trout red blood cells in vitro: adrenergic inhibition and the influence of oxygenation status

Chris M. Wood, Heather Simmons

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9 Scopus citations


This study employed a recently developed radioisotopic assay (Wood and Perry 1991) to examine the inhibition, induced by catecholamines, of the conversion of plasma HCO3- to CO2 in acidotic trout blood, and the influence of oxygenation status on the response. Blood was incubated in vitro at PCO2= 2 torr, and 10-6 M noradrenaline was employed as the adrenergic stimulus. In particular we investigated whether the inhibition of plasma HCO3- conversion could be explained by a limited supply of H+s for the intracellular HCO3- dehydration reaction because of competition by the adrenergically activated Na/H+ exchanger. Hypoxia (PO2= 15 torr) was employed as a tool to intensify this competition. Hypoxia raised RBC pHi, pHe, and plasma total CO2 concentration (CCO2) by the Haldane effect, and increased the magnitude of Na+/H+ activation, expressed as the change in the transmembrane pH gradient (pHe-pHi). However hypoxia did not alter the inhibition of the conversion of plasma HCO3- to CO2 caused by noradrenaline. Hypoxia itself stimulated the RBC-mediated conversion of plasma HCO3- to CO2 by about 20% in the presence or absence of noradrenaline. The conversion rate was strongly correlated with pHe, pHe-pHi, and plasma CCO2 in these experiments, but not with pHi. We conclude that adrenergically mediated inhibition in the conversion of plasma HCO3- to CO2 by trout RBCs is not due to competitive limitation on intracellular H+s, but rather to changes in the electrochemical gradient for HCO3- entry and/or to CO2 recycling from plasma to RBC. The deoxygenated condition helps to promote CO2 excretion at the level of the RBC.

Original languageEnglish
Pages (from-to)445-454
Number of pages10
JournalFish Physiology and Biochemistry
Issue number6
StatePublished - Mar 1 1994



  • bicarbonate dehydration reaction
  • catecholamines
  • chloride-bicarbonate exchange
  • CO excretion
  • hypoxia
  • intracellular pH
  • plasma HCO
  • rainbow trout
  • red blood cells
  • sodium-proton exchange

ASJC Scopus subject areas

  • Physiology (medical)
  • Physiology
  • Biochemistry
  • Biochemistry, Genetics and Molecular Biology(all)
  • Aquatic Science

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