Mean Myoglobin Oxygen Tension in Skeletal and Cardiac Muscle

Abstract

We have utilized the concept first developed by Millikan (1936, 1937) that myoglobin may be a useful indicator of intracellular oxygen tension. We have not made spectrophotometric measurements of oxymyoglobin % saturation, as did Millikan, since the presence of hemoglobin interferes with this measurement, but instead compute a mean myoglobin oxygen tension from measurements of carboxymyoglobin saturation (MBCO). This method has been described previously (Coburn and Mayers, 1971; Coburn et al, 1973). The basis of the method is illustrated in Fig. 1. Binding of O₂ and CO to myoglobin is competitive, therefore, at a given partial pressure of CO, MBCO is a function of the oxygen tension in proximity to myoglobin molecules. This figure also illustrates that mean tissue Pco is equal to mean capillary Pco since CO is neither produced nor consumed at a significant rate.