Dependence of O2 uptake on tissue Po2: experiments in intact excised rat skeletal muscle.

Oxygen uptake (M) at different surface O2 pressures (Po) was measured in intact, excised rat skeletal muscle suspended in the gas phase. Above a critical value of Po(Pc), M was apparently independent of Po; below Pc, M declined in close proportion to the square root of Po. This experimental relationship was compared with predictions based on the model of Warburg (1923) which assumes the tissue to be homogeneous in respect of its metabolic rate, diffusivity and geometry. The good agreement between the Warburg model and the experimental values suggests that the assumptions underlying this model are justified.