Equivalent pore modeling: vesicles and channels.

The methods used to estimate equivalent pores in capillary walls using lymph protein flux analyses are presented. The capillary walls in several different organs can be described by a two-pore model that incorporates pores of radii 50-80 and 200-250 A. The most likely ultrastructural correlates of these physiological pores appear to be the transendothelial channels. In addition, the positive charge associated with endogenous protein transport in intestinal and lung capillaries may reflect the positive charge located on the inner walls of the transendothelial channel.