Recombinant human tumor necrosis factor depresses serum iron in mice

Recently many findings about the physiological and biochemical functions of recombinant human tumor necrosis factor (rHu-TNF) have been reported. In the present study, the effect of rHu-TNF on serum iron in C3H/HeN and C57BL/6 mice was determined. Blood samples were obtained before intravenous injection of rHu-TNF, and also at various times after the injection. Results from five experiments showed that the serum iron was depressed between 1/3 to 1/5 of that of untreated mice 4 to 24 h after injection of 5 or 10 micrograms of rHu-TNF. The low level persisted for 33 h, rebounded at 48 to 72 h, and returned to normal by 96 h after the injection. Serum iron was determined by the colorimetric method using the sensitive reagent, ferrozine (3-(2-pyridyl)-5,6-bis(4-sulfophenyl)-1,2,4-triazine. We believe that this is the first report of depression of serum iron in mice by intravenous injection of rHu-TNF. The physiological role of repressed serum iron in the in vivo response to TNF remains to be established.