Chelation of endosomal labile iron generated by adsorptive endocytosis of CALG-Fe complexes in different cell types. HepG2 (top), H9C2 (middle), and J774 (bottom) cells were loaded with CALG-Fe complexes (50 μM) by incubating them in growth medium supplemented with 1% serum albumin. The depicted images represent overlays of images obtained before and after addition of 50 μM SIH (1-15 minutes, viewed by epifluorescence and merged with phase microscopy). All incubations and perfusions were carried out at 37°C. Probenecid (0.5 mM) was supplemented in order to minimize leakage of the calcein (CAL). The mean fluorescence intensity levels in the various cells following similar loading treatments and analyzed with equivalent parameters were (in relative terms) 10 for J774, 3 for H9C2, and 1 for HepG2.