Radiochromatographic Identification of Thyroxin

Iodine administered orally as NaI131 associates with two electrophoretically identifiable serum proteins (1-4). It appears first with the albumin fraction where it is associated with the slower moving component. It is later found in a zone of low protein concentration just ahead of alpha-2 globulin. This behavior was observed in the serum from both euthyroid and hyperthyroid subjects. However, in hyperthyroid subjects the tracer iodine concentrated faster, attained higher levels, and declined more rapidly in this alpha globulin zone (5). This suggested that the hormonal iodine may be associated with this specific protein. The exact nature of this iodine compound is unsettled although the presence of thyroxin and more recently 3:5:3'-L-triiodothyronine (6) has been demonstrated in whole serum. The purpose of this present paper is to report the radiochromatographic analysis of iodine containing amino acids associated with an alpha globulin fraction separated by starch electrophoresis.