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Immunofluorescent subcellular localization of cytochrome c in Cr(VI)-treated human fibroblasts (BJ-hTERT) undergoing apoptosis. The intracellular cytochrome c staining pattern was analyzed by confocal laser scanning microscopy and highlights diffusion of cytochrome c throughout the cytoplasm.

Cytochrome c is normally localized within mitochrondria causing a punctate staining pattern within control cells, but it is released from mitochondria to the cytosol upon induction of apoptosis with Cr(VI) causing the diffuse staining pattern shown here. For details, see the article by D. Pritchard et al. in this issue.