Myocardial myoglobin oxygen tension.

COBURN, R. F., F. PLOEGMAKERS, P. GONDRIE, AND R. ABBOUD. Myocardial myoglobin oxygen tension. Am. J. Physiol. 224(4): 870-876. 1973.-We have applied our method of estimating mean myoglobin oxygen tension from measurements of carbon monoxide binding to myoglobin to the in vivo canine myocardium. Carbon monoxide binding to myoglobin was determined with measurements of 14C0 in myocardial biopsy specimens. The quantity of carbon monoxide bound to myoglobin, expressed as a ratio of carboxymyoglobin to carboxyhemoglobin, remained constant over a wide range of arterial oxygen tensions, above 30-35 mm Hg. Mean myoglobin oxygen tensions at normal arterial oxygen tensions were computed to be 4-6 mm Hg. Fine control of intracellular oxygen tension was demonstrated, since only small changes in mean myoglobin oxygen tension occurred with large changes in arterial oxygen tension, as long as arterial oxygen tensions remained greater than 30-35 mm Hg. With acute progressive hypoxemia, influx of carbon monoxide into myocardium occurred at a time when arterial oxygen tension fell to less than 30-35 mm Hg. This influx is thought to be due to a fall in intracellular oxygen tension, and evidence was obtained that it occurred at a time during acute progressive hypoxemia when intracellular oxygen tensions limited aerobic metabolism.