COPPER IS REQUIRED TO MAINTAIN CU ZN-SUPEROXIDE DISMUTASE ACTIVITY DURING HL-60 CELL-DIFFERENTIATION/

The objective of these studies was to characterize the relationship be tween copper levels and Cu/Zn superoxide dismutase (Cu/Zn-SOD) during cellular differentiation. It was hypothesized that the decrease in Cu/ Zn-SOD activity that accompanied differentiation would be reversed by supplementing the culture medium with copper. HL-60 cells, a human pro myelocytic cell line, were induced to differentiate with retinoic acid and were concurrently supplemented with copper or a copper chelator, tetraethylenepentamine. The results showed that retinoic acid-treated cells contained more copper after differentiation. When the medium was supplemented with copper during retinoic acid treatment, the differen tiating cells accumulated more copper than the nondifferentiating cell s. Differentiation was accompanied by a significant reduction in Cu/Zn -SOD activity and a slight reduction in Cu/Zn-SOD protein. Activity re turned to control values when an extracellular source of copper was pr ovided. Incubation of retinoic acid-treated cells with the chelator sh owed that they lost proportionally less copper than the noninduced con trols. Levels of Cu/Zn-SOD protein were not affected by the copper or chelator treatments. It was concluded that the requirement of differen tiating HL-60 cells for copper is not related to providing copper for Cu/Zn-SOD activity. If a supplemental source is not supplied in the me dium, then the cells may acquire copper from an intracellular source, namely Cu/Zn-SOD.