Newly delivered transferrin iron and oxidative cell injury

Cell iron status was assessed in terms of its capacity to mediate cell injury by pro-oxidants. Cultured K562 cells, which maintain a stable cytosolic labile iron pool (LIP) of < 0.5 mu M, underwent distinct changes after short exposures to transferrin (Tf) followed by t-butyl hydroperoxide (TBHP): (a) rise in LIP, detectable fluorimetrically (b) increased lipid peroxidation and (c) eventual cell death: All of these effects were inhibited by weak bases or iron chelators, Similarly, hydrogen peroxide caused rises in both LIP and oxidant species detectable with 2',7'-dichlorofluorescin diacetate, which were enhanced by preincubation with Tf. The Tf-delivered iron disappeared from LIP and the TBHP-reactive pool with a t(1/2) < 30 min. The results indicate that the catalytic potential of iron is highest while in transit between endosomes and cytosolic ligands. (C) 1997 Federation of European Biochemical Societies.