Myoglobin O2 tension determined from measurement of carboxymyoglobin in skeletal muscle.

COBURN, R. F., AND L. B. MAYERS. Myoglobin 02 tension determined from measurements of carboxymyoglobin in skeletal muscle. Am. J. Physiol. 220(l) : 66-74. 1971.-We have developed a method of estimating muscle intracellular oxygen tension in vivo, using myoglobin as an oxygen tension indicator. The method is based on the competition of oxygen and carbon monoxide for binding sites on myoglobin and allows calculation of the mean 02 tension in equilibrium with myoglobin from measurements of mean muscle PCO and carboxymyoglobin percent saturation. In our experiments the partition of CO between blood and muscle remained constant when the arterial oxygen tension ranged from 40 mm Hg to over 700 mm Hg, but CO shifted out of circulating blood into muscle when the arterial POT fell below 40 mm Hg. The mean myoglobin 02 tension in resting canine hamstring muscle at less than 1 y0 blood carboxyhemoglobin percent saturation and %ormal” arterial Paz (67-l 20 mm Hg) was 4.7 & (SE) 0.3 mm Hg. The mean myoglobin 02 tension decreased approximately 1.5 mm Hg as the arterial Paz was lowered from 490 to 40 mm Hg. When the arterial POT fell below 35-40 mm Hg, the mean myoglobin 02 tension was 0.5-l .5 mm Hg.