Control of respiration in skeletal muscle at rest.

The suggestion is made that, under resting conditions in situ, muscle cell respiration is dependent on the way O2 and substrates are distributed to the cells by the microcirculation. (Delivery is measured as arterial-blood concentration multiplied by flow to the organ.) Microscale heterogeneity of this distribution, which is more marked but less stable than the more easily demonstrated larger-scale heterogeneity (0.1 to 0.5-g sampling grain), might indeed ration O2 and substrates in a large population of the cells of a resting organ at any given moment, and microscale heterogeneity of distribution may thus take part in the normal control of cell respiration.