Determination of diffusivity of oxygen and carbon dioxide in respiring tissue: results in rat skeletal muscle.

Gas transfer rates for O2 and CO2 through freshly excised respiring rat abdominal muscle were measured. The tissue separated as a thin membrane two chambers, one of which was ventilated with a constant gas mixture. The other chamber was closed and the time course of changes of PO2 and PCO2, initially set at varied levels, was followed by electrodes. A plot of rate of change of PO2 and PCO2 in the closed chamber against the partial pressure difference across the tissue yielded both Krogh's diffusion constant, KO2 and KCO2, and metabolic rate of tissue, i.e. specific O2 consumption and CO2 production, mo2 and mco2. The mean values at 37 degrees C, KO2 = 1.31 x 10(-9) mMol-cm-1-min-1-torr-1 and KCO2 = 28.0 x 10(-9) mMol-cm-1-min-1-torr-1, did not differ significantly from values determined by other authors in various tissue preparations in which metabolism had been suppressed. Average O2 consumption, mo2 = 0.87 mMol-min-1-L-1, was not different from the values obtained in the same tissue by the Warbung manometric method, 0.74 mMol-min-1-L-1. The mean respiratory quotient, calculated as the ratio of mean CO2 production and mean O2 consumption, was 0.85.