Permeability of Connective Tissue Linings Isolated from Implanted Capsules

Quantification of the permeability of connective tissue linings isolated from implanted capsules was achieved by two types of experiments. The objective of the first type was to determine the restriction offered by the lining to diffusion of 'I-labeled human serum albumin. The restricted diffusion coefficient of albumin with respect to the connective tissue lining the luminal capsule surface (internal lining) averaged 3.0 x 10~ ± 0.4 x 10~ cmVsec in ten experiments indicating that the rate of migration of albumin across the structure was 35% of its free diffusion rate in water. In contrast, the albumin diffusion coefficient obtained for the abluminal (external) lining suggested that diffusion of albumin through this structure was 73% of the free diffusion rate in water. The objective of the second type of experiment was to determine solute reflection coefficients for inulin, serum albumin, and y-globulin with respect to the internal and external linings. For the internal lining, the reflection coefficients were: inulin 0.07, albumin 0.23, and y-globulin 0.53. The external lining showed greater leakiness as evidenced by its lower reflection coefficient for a given molecule and its higher hydraulic conductivity. An equivalent pore calculation resulted in a calculated pore radius of 250-350 A for the internal lining and a calculated pore radius of 500-600 A for the external lining. The ineffectiveness of the leaky capsule lining in transmitting oncotic pressure suggests that under normal conditions the capsule measures interstitial hydrostatic pressure rather than oncotic pressure.