The distribution of diffusion distances in the gastrocnemius muscle of various mammals during maturation.

Large changes in fiber size, capillary density and capillary/fiber architecture occur during maturation of mammalian skeletal muscle. To examine the effect of these changes on oxygen diffusion distance, the mean (R) and maximal (R95) distances from the capillary to the tissue were measured in the gastrocnemius of maturing guinea pigs, rats and dogs. Hyperbolic relationships between capillary density and R and between capillary density and R95 were found for the combined data from these three species. The R and R95 increased with decreasing CD in growing guinea pigs and rats, but they remained constant in dogs. Statistical analyses showed that the capillaries in this muscle in all three species tended to be distributed in ordered arrays. These anatomical measurements are discussed in relation to their potential physiological impact on oxygen delivery to tissues.