AN ANALYSIS OF CARBON-DIOXIDE TRANSPORT IN ARTERIAL AND VENOUS-BLOOD OF THE RAINBOW-TROUT, ONCORHYNCHUS-MYKISS, FOLLOWING EXHAUSTIVE EXERCISE

Arterial and venous cannulations were used to examine the characterist ics of CO2 transport in pre and post branchial blood both at rest and during recovery from exercise. As in previous studies, exercise caused a marked decrease in the extracellular pH (pH(e)) in both arterial an d venous blood. Except for a transient increase in venous blood immedi ately following exercise, plasma total CO2 ([C(CO2)]t.pl) and whole bl ood total CO2 ([C(CO2)]wb) decreased in both arterial and venous blood during recovery. Exercise also resulted in an increase in red blood c ell total CO2 concentration ([C(CO2)]i) and in the partial pressure of CO2 (P(CO2)) in both arterial and venous blood. Activation of the adr energic mechanism at the level of the red blood cell likely contribute d to the increases observed in ([C(CO2)]i) following exercise. At rest , the majority of the total [C(CO2)] carried in arterial and venous bl ood could be attributed to the plasma, with 2 and 9% carried in the re d blood cells, respectively. However, exercise resulted in an increase in the percentage of CO2 carried within the red blood cell to 13.5 an d 20% in arterial and venous blood, respectively. The total CO2 differ ence between pre and post branchial blood also increased following exe rcise suggesting an increase in CO2 excretion.