Studies of I131-Albumin Catabolism and Distribution in Normal Young Male Adults*

Studies of I13'-albumin catabolism and distribution are appearing in rapidly increasing numbers in current literature.The data for normal human subjects reported from various laboratories differ considerably in mode of analysis and in results ob- tained.In normal subjects the observed "half-life" of I'31-albumin has ranged from below 10 to above 20 days (1-15), and the ratio of the amount of albumin contained extravascularly to that present in the plasma has been calculated as ranging from 1 to 4.5 (6, 7, 15-17).Although these wide vari- ations are due to many factors, the major causes appear to be these: 1) variable degrees of denaturation incurred during the preparation of the protein and its radioisotopic labeling, perhaps de- tectable only through biological testing; 2) vari- able lengths of study periods, many being too short to allow metabolic trends to be fully realized; and 3) differing mathematical approaches to the analysis of data, each requiring assumptions of variable validity.With the availability of im- proved I131-albumin preparations, it can be antici- pated that greater efforts will be directed toward the investigation of albumin catabolism and distri- * Supported in part by research grants from the Na- tional Institute of Arthritis and Metabolic Diseases (A-173, A-2542, A-2803).