Whole body capillary exchange of albumin.

Analyzed versus the large plasma marker of fibrinogen, initial albumin plasma disappearance in man or animals is sharply biphasic. Albumin uptake in skin, muscle and viscera follow the same pattern, suggesting serial barriers to albumin efflux in these tissues, i.e., a capillary membrane barrier and an interstitial barrier. The transport across the membrane is rapid, in both directions and probably mediated by diffusion, while interstitial transport may be slow, mainly unilateral and mainly convective. This implies the interstitial barrier and not the capillary membrane to be the rate limiting step of total plasma to lymph albumin transport. The distribution of efflux indicates whole body plasma disappearance to reflect mainly the uptake in muscle, lung, skin, and gut, while the highly perfused tissues of heart, kidney and sinusoid tissue have smaller influence due to their lower body masses.