Initial equilibration of albumin and IgG in rabbit hind paw skin and lymph.

To determine if the interstitial distribution of plasma proteins influences transport from plasma to lymph, the initial plasma-to-extravascular and plasma-to-lymph equilibrations for 131I-labeled rabbit albumin and 125I-labeled rabbit IgG were compared in hind paw heel skin of anesthetized New Zealand White rabbits. Plasma specific activities were maintained constant with time using continuous infusions. The plasma space in skin samples taken at the end of the experiment was estimated by a 3-min accumulation of 59Fe-labeled bovine transferrin. Albumin and IgG concentrations in plasma, lymph, and skin were determined by rocket electroimmunoassay. The lymph specific activity relative to that of plasma for the larger sized IgG was significantly greater (P less than 0.01) than that for albumin during the initial 8 hr of equilibration. The tissue specific activity relative to that of plasma for IgG was significantly less (P less than 0.01) than that for albumin. The distribution space at lymph concentration for both proteins was 1 ml/g dry skin wt, indicating similar excluded volumes. These data are consistent with the hypothesis that convective movement of plasma proteins through the interstitium affects lymph equilibration while diffusion affects tissue equilibration.