Fig 1.
Oxygen equilibrium curves (OECs) generated at 0.25, 0.5, 1.0, 2.0, and 4.0% CO2 with stepwise decreases in PO2 (mmHg) from 160 to 0 mmHg (balance N2) for rainbow trout rinsed RBCs (panel A).
The ΔpHe relative to the 0.25% CO2 curve (black, pHe = 8.01) is also noted for each treatment. Data are means ±S.E.M. Brackets indicate no statistically significant effect of CO2 at the respective PO2. Dashed lines extend from 50% Hb-O2 saturation to indicate the P50 for each OEC. In panel B, the magnitude of the right-shift of the OEC for a given pH change (ΔpH represented as different colours) is represented as ΔPO2 over each Hb-O2 saturation for a Bohr effect Hb system (human, dashed lines between 20 and 80% Hb-O2 saturation only) or a Root effect Hb system (rainbow trout, solid lines).
Table 1.
Effects of carbon dioxide (% CO2) on haematological parameters, pH and oxygen transport-related variables for blood of rainbow trout.
Fig 2.
The degree to which O2 release from Hb is enhanced for a given ΔpH for a Bohr effect Hb system (human, panel A) and a Root effect Hb system (rainbow trout, panel B).
The increase in O2 release with respective right-shifts in the OECs is represented by vertical double arrows here and as a percent increase over what is possible without the right shift in the text (see above section “Series 2: Differences in ΔPO2…” for details).
Fig 3.
Model estimates for enhanced O2 release from Hb (as a %) in rainbow trout under normoxic conditions, various levels of sustained exercise, and various levels of hypoxia at two different simulated ∆pHa-v (panels A and B) compared to when there is no right shift in the oxygen equilibrium curve (OEC).
The PaO2 values corresponding to arterial Hb-O2 saturations (indicated by red cells) were derived from the resting curve of Fig 1A. Calculated values at each combination of arterial Hb-O2 saturation (red cells) and venous PO2 (PvO2) values (blue cells) represent the % increase in O2 delivery (white cells) over what is possible without a right-shift in the OEC. Curves for ∆pH = -0.2 (panel A) and ∆pH = -0.55 (panel B) were used for this model. For scenarios where the Pa-vO2 difference was less than 5 mmHg (deemed unrealistic), no data are shown (—).