Abstract
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 language | English (US) |
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Pages (from-to) | 445-454 |
Number of pages | 10 |
Journal | Fish Physiology and Biochemistry |
Volume | 12 |
Issue number | 6 |
DOIs | |
State | Published - Mar 1 1994 |
Keywords
- 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