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

Summary

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 ofP _{O 2}andP _{CO 2}, initially set at varied levels, was followed by electrodes. A plot of rate of change ofP _{O 2} andP _{CO 2} in the closed chamber against the partial pressure difference across the tissue yielded both Krogh's diffusion constant,K _{O 2} andK _{CO 2}, and metabolic rate of tissue, i. e. specific O₂ consumption and CO₂ production,$\dot m_{{\text{O}}_{\text{2}} }$ and$\dot m_{{\text{CO}}_{\text{2}} }$.

The mean values at 37°C,K _{O 2}=1.31×10⁻⁹ mMol·cm⁻¹·min⁻¹·torr⁻¹ andK _{CO 2}=28.0×10⁻⁹ 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,$\dot m_{{\text{O}}_{\text{2}} }$, 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.