THE APPARENT EXTRACELLULAR SPACE OF MAMMALIAN SKELETAL MUSCLE: A COMPARISON OF THE INULIN SPACE IN NORMAL AND DYSTROPHIC MOUSE TISSUES
The apparent extracellular volumes of the muscles from young normal and dystrophic mice have been estimated, using inulin dilution techniques. The inulin spaces were measured in the muscle both following injection of inulin in vivo and after soaking of excised tissues in a solution containing inulin. Comparisons were made between muscles of different size from the same animal as well as from different animals whose age, and consequently muscle size, varied. In all cases it has been found that the inulin space decreases with increasing muscle size. Similar results have been obtained by others with toad sartorii. The inulin space in muscles from dystrophic mice is larger than that of comparable normal tissues, and the dependence on muscle size, although similar to normal, is more pronounced. The results suggest that the dystrophic cells are permeable to inulin, and the question that some small permeability may be present also in normal tissue is considered.