CERULOPLASMIN, TRANSFERRIN AND APOTRANSFERRIN FACILITATE IRON RELEASEFROM HUMAN LIVER-CELLS

The rate of iron release from HepG2 liver cells was increased not only by extracellular apotransferrin, but also by diferric transferrin, in a non-additive, concentration-dependent manner and to a similar magni tude. This suggests that rapid equilibration between receptor-mediated uptake and the release process determines net iron retention by the l iver, Release was also accelerated by ceruloplasmin; most importantly, the effect of this protein was greatest when iron release was occurri ng rapidly, stimulated by apotransferrin, or under conditions of Limit ed oxygen. Thus iron release involves both apotransferrin and ferrotra nsferrin, with ceruloplasmin playing a role in tissues with limited ox ygen supply, as in the liver in vivo. (C) 1997 Federation of European Biochemical Societies.