Tissue Distribution of I131 Labeled Human Serum Albumin Following Intravenous Administration

Previous studies utilizing I'sl' labeled human serum albumin have revealed that approximately 60 per cent of the total exchangeable albumin of nonedematous subjects is in extravascular loca- tions (1, 2). Following intravenous administra- tion, approximately 4 to 7 days are required for essentially complete equilibration of the labeled albumin between plasma and extravascular tissues (2, 3). In almost all cases the plasma disappearance curves, appropriately corrected for metabolic degradation, manifest two major components with half times of approximately 3 to 5 hours and 24 to 30 hours, respectively, suggesting that there are at least two groups of albumin containing extravascu- lar compartments which equilibrate with plasma at different rates (2, 3). However, the distribu- tion of extravascular albumin and the anatomical sites of the rapidly and slowly equilibrating ex- travascular compartments have not yet been quan- titatively defined although previous studies utiliz- ing massive doses of heterologous serum proteins in rabbits established the presence of these pro- teins in the extravascular phase of muscle 48 hours after intravenous administration (4).