Radioimmunoelectrophoretic analysis of proteins binding 3, 3', 5'-triiodothyronine in human serum.

The binding of purified 131I-3, 3', 5'-triiodothyronine (reverse T3) (rT3) to normal human serum components was investigated by a radioimmunoelectrophoretic technique. When anti-whole human serum was used, five distinct arcs of radioactivity were observed. Evidence was obtained that five of these radioactive arcs were not artifacts, but were due to components binding rT3. From the radioimmunoelectrophoretic patterns with specific antisera, five of these components were identified as thyroxine binding prealbumin, albumin, thyroxine binding globulin (TBG) and alpha 1-and beta-lipoproteins. No radioactive arc of TBG was detected in serum from a patient with TBG deficiency.