In vitro carbon dioxide excretion from erythrocytes of two species of Antarctic fishes and its inhibition by catecholamines

This study was designed to investigate whether the blood of Pagothenia borc hgrevinki exhibits a Haldane effect, and whether activation of a Na+/H+ ant iporter increases transport of intracellular protons and Bohr protons out o f the erythrocytes resulting in inhibition of CO2 excretion in both P. borc hgrevinki and Dissostichus mawsoni. When carbon dioxide dissociation curves were determined from blood samples pooled from three fish under oxygenated and deoxygenated conditions a Haldane effect was observed. Using an in vit ro CO2 excretion assay, the rate of HCO3- dehydration was determined on blo od and plasma equilibrated under an N-2 atmosphere then rapidly oxygenated with air in the presence of 10(-5) M noradrenaline or acetazolamide (10(-4) M). Whole blood and plasma from P. borchgrevinki and D. mawsoni were equil ibrated with 0.5% CO2 in air and assayed in the presence of 10(-5) M noradr enaline. Erythrocyte CO2 excretion rates were depressed significantly by no radrenaline in both species. The whole blood HCO3- dehydration rate was dep ressed significantly following rapid oxygenation in the presence of acetazo lamide indicating that the pathway of CO2 excretion included activation of intracellular carbonic anhydrase and an adrenergic receptor. (C) 2000 The F isheries Society of the British Isles.