Iodine metabolism and iodothyronine (T3 and T4) binding in human polymorphonuclear leucocytes in vitro

Surviving human polymorphonuclear leucocytes (PMNL) were found to incorporate and metabolize 125I in vitro. After incubation the metabolized iodine may be found in three different fractions which may be separated by Sephadex G-200 column chromatography. The first fraction consists of deoxyribonucleoproteins and specifically binds T3 (Bmax) 4 x 10(-12) mol mg-1 protein; Ka (4.5 x 10(11) mol-1 mg) and T4 (Bmax) 13 x 10(-12) mol mg-1 protein; Ka (0.77 x 10(11) mol-1 mg). The second fraction binds iodine and T4 by a non displaceable manner. It appears to be acid precipitable and possibly of iodoprotein nature. The third fraction of iodinated molecules was further analyzed with the aid of Sephadex G-10 column chromatography and it was found that these compounds may correspond to iodothyronines, as concluded from their physicochemical characters. The addition of T3 or T4 or TSH reduced the radioactivity associated presumably to nucleoproteins and iodoproteins. These experiments suggest a possibility of intracellular synthesis and macromolecular binding of iodothyronine-like compounds in PMNL and the influence of external T3, T4 and TSH.