Endolysosomes were more abundant and contained higher levels of Fe2+ when located further away from plasma membranes: (a) Representative magnified confocal image (inset) of an U87MG cell labeled with FeRhoNox-1 for [Fe2+]el, LysoTracker for endolysosomes, and CellLight-PM for plasma membranes. (b) Endolysosomes were more abundant when located furthest away from plasma membranes. (c) The cell depicted in (a) above was reconstructed with Imaris software (version 9.5, Oxford instruments) to demonstrate [Fe2+]el relative to endolysosome locations. (d) Endolysosomes contained higher levels of Fe2+ when located furthest away from plasma membranes. Scale bars are 5 μm. Each data point represents the mean fluorescence intensity of endolysosomes per cell measured from 10 cells (n = 50). (b) F(4, 20) = 286.3, p < 0.0001; (d) F(4, 20) = 107, p < 0.0001