Self Diffusion in Cells and Tissues.

Diffusion measurements in three types of frog muscle have yielded a constant value of 1.7 x 10 to the minus 5th power sq cmsec at the shortest times, indicating that the intracellular material does not have a high microviscosity, nor does it contain effective diffusion barriers. The diffusion coefficients at longer times indicate an outer membrane permeability of 0.01 cmsec. This work has been accepted in Biophysical Journal. Diffusion measurements of water in packed red cells indicated a much higher microviscosity than is the case in frog muscle. The permeability of 0.01 cmsec is in good agreement with that obtained by osmotic shock and by NMR spin-relaxation methods.