Oxygen binding and acid base status of the blood from the freshwater turtle, Phrynops hilarii

1. 1. Oxygenation studies with the whole blood of Phrynops hilarii show a P₅₀ of 38 torr at extracellular pH (pHe) of 7.4 which corresponds to an intracellular pH (pHi) of 7.05 at 25°C. 2. 2. The blood CO₂ Bohr effect was -0.56 when related to pHi. 3. 3. pHi is related to pHe by the following equation: pHi = 0.75.pHe + 1.54 (r = 0.99); pHi = 0.72.pHe + 1.72 (r = 0.96) at 10 and 25°C respectively. Blood pH, pHe, for 25°C, was 7.519 ± 0.254 (n = 6). 4. 4. Blood gas partial pressures were: pCO₂ = 25.8 ± 3.8 torr (n = 6); pO₂ = 61.7 ± 21.2 torr (n = 6). 5. 5. The major red cell phosphates, in mmole/l erythrocytes, n = 6, were: ATP (3.66 ± 0.86); GTP (0.53 ± 0.28); 2.3-DPG (0.32 ± 0.12) and inorganic phosphates (2.00 ± 0.35). 6. 6. The plasma inorganic ion composition, n = 6, was, in mEq/l: K⁺ (3.04 ± 0.40); Na⁺ (148.4 ± 12.6); Ca²⁺ (4.75 ± 1.32); Cl (106.6 ± 5.0). 7. 7. Additional blood parameters of interest (n = 6) were: lactate (2.07 ± 1.72 mM in plasma); erythrocytes/mm³ (416 × 10³ ± 4.6 × 10³); leucocytes/mm³ (4636 ± 2618); haematocrit (%) (14.5 ± 3.6); haemoglobin, g/dl (3.2 ± 0.5); plasma protein g/dl (4.4 ± 0.4); osmolarity (293 ± 10 mOsm/l). 8. 8. The non-bicarbonate buffer value was -22.6 mmol/kg H₂O/pH. 9. 9. For a constant CO₂ content, ΔpHe Δt = 0.0141 ± 0.002 (n = 18) and ΔpHi Δt = 0.0157 ± 0.003 (n = 18).