Fig. 3. (A) Steady-state oxygen uptake of suspensions of cardiac myocytes as functions of carbon monoxide partial pressure. Oxygen uptake is normalized, taking the uninhibited rate in each experiment as unity. Oxygen partial pressure (P_O2) is equal to 10.6–12.0 kPa (80–90 torr) or 13.3–16.0 kPa (100–120 torr). The oxymyoglobin-dependent portion of the oxygen uptake is taken as the difference between the uninhibited rate and the plateau value at high carbon monoxide partial pressure (P_CO). Carbon monoxide inhibition of cytochrome oxidase becomes evident above P_CO=80 kPa (600 torr). Reproduced from Wittenberg and Wittenberg (1987). (B) Oxymyoglobin-dependent oxygen uptake of suspensions of cardiac myocytes as functions of mole fraction carbon monoxide myoglobin (MbCO). Since myoglobin (Mb) is essentially fully occupied by ligands, mole fraction MbO₂ = 1 –mole fraction MbCO. In different experiments, P_O2 is equal to 5.3–8.0 kPa (40–60 torr), 9.3–12.0 kPa (70–90 torr), 13.3–16.0 kPa (100–120 torr) or 45 kPa (340 torr). Reproduced from Wittenberg and Wittenberg (1987).

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