Kinetics of iron efflux from SH-SY5Y cells. SH-SY5Y cells were cultured for 2 days with varied amounts of iron as described in Figure 1A. The culture medium was changed to fresh DMEM and the kinetic of iron exit from the cells was followed by determining the concentration of iron in the medium by absorption spectrometry (A). Data is means ± SD from 3 experiments. The efflux rate, obtained from the slope of the curves in Figure 7A, was plotted against iron concentration during the 2-day culture period (B). In C, the efflux rate was plotted against the density of the 65.3 KDa or 122.1 KDa bands. To that end, the 65.3 KDa or 122.1 KDa bands shown in Figure 5 were quantified by densitometry and paired with the efflux rates determined in Figure 7A at the same iron concentrations. A good correlation between efflux rate and the presence of the 122.1 KDa band was observed.