Permeability of interstitial space of muscle (rat diaphragm) to solutes of different molecular weights.

The transport characteristics of muscle interstitial space were determined using an isolated rat diaphragm preparation. Permeability of the interstitial space for extracellular solutes is one-thirtieth to one-fiftieth that of an equivalent thickness of water. However, most of this low permeability can be accounted for by correcting for the tortuosity and relative volume of interstitial space. The estimated diffusivity of solutes (mol. wt. 100-70,000) in the interstitial space of muscle is only about one-half to one-fifth less than in water alone.