Ioxynil and 3,5,3'-triiodothyronine: comparison of binding to human plasma proteins.

Ioxynil, an iodine-containing compound with structural similarity to T3 affects the thyroids of experimental animals. Binding to human plasma proteins was compared with that of T3, to gain insight into possible effects in humans. After incubating human serum with [125I]ioxynil, 2DIEP against anti-whole human serum and rocket immunoelectrophoresis against anti-TBPA, albumin or TBG were carried out. Ioxynil bound to TBPA but not to TBG nor albumin. The Ka calculated for the TBPA-ioxynil complex was 2.6 x 10(6) l.mol-1. Ioxynil competed for the iodothyronine-binding sites of TBPA.