INTERSTITIAL DIFFUSION OF MACROMOLECULES IN THE RAT MESENTERY

Apparent diffusion coefficients of fluorescein isothiocyanate (FITC)-labeled dextrans (Mw 3400-41,200) and rat serum albumin (RSA-FITC) were measured in the interstitial space of the rat mesentery. Average ratios of apparent diffusion coefficient to free diffusion coefficient for the dextrans ranged from 0.26 for dextran 3400 to 0.033 for dextran 41,200 and 0.073 for RSA-FITC. These values are lower than those reported for loose connective tissue (umbilical cord) but greater than those from dense connective tissue (cartilage). The apparent diffusion coefficient for RSA-FITC was approximately one-half the apparent diffusion coefficient of FITC-dextran having the same free diffusion coefficient (and thus the same Stokes radius). Mathematical models describing solute diffusion in gels or glycosaminoglycan solutions as a function of solute size did not give a good fit to the data but indicated that the presence of a relatively dense interstitial matrix is required in order to explain the data. © 1979.