Effects of cobalt on haem proteins of erythropoietin‐producing HepG2 cells in multicellular spheroid culture

Abstract

The hypoxia-induced increase of spectrophotometrically measured light absorption at 560 nm, considered as reduced cytochrome b, in HepG2 cells is diminished after exposure to cobalt chloride (50 or 100 μM) for 18–36h. The redox state of cytochrome c and cytochrome aa ₃, however, remains stable, indicating a particular affinity of cytochrome b for cobalt. Erythropoietin production of HepG2 cells increases after application of cobalt chloride, whereas H₂O₂ production, as measured by the dihydrorhodamine technique, decreases. It is concluded that cobalt stimulates a signal cascade with cytochrome b as receptor and H₂O₂ as second messenger for regulating erythropoietin production.