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Related Experiment Videos

Ascorbate-mediated transmembrane electron transport and ascorbate uptake in leukemic cell lines are two different

E Schweinzer1, H Goldenberg

  • 1Institut für Medizinische Chemie, Universität Wien, Austria.

European Journal of Biochemistry
|June 15, 1992
PubMed
Summary
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Leukemic cells catalyze extracellular oxidant reduction using ascorbate, independent of cellular uptake. This membrane redox cycle, sensitive to inhibitors, highlights a novel cellular mechanism for managing oxidative stress.

Area of Science:

  • Biochemistry
  • Cell Biology
  • Hematology

Background:

  • K562 and U937 leukemic cells possess mechanisms for managing extracellular oxidative stress.
  • Ascorbate (vitamin C) is a known antioxidant with complex interactions within biological systems.

Purpose of the Study:

  • To investigate the role of ascorbate in transmembrane reduction of extracellular oxidants by K562 and U937 leukemic cells.
  • To elucidate the mechanism by which ascorbate stimulates this reduction process.

Main Methods:

  • Assessing the effect of ascorbate and dehydroascorbate on oxidant reduction by leukemic cells.
  • Investigating the involvement of cellular transport mechanisms for ascorbate.
  • Evaluating the kinetics and affinity of the membrane redox cycle for ascorbate.

Related Experiment Videos

  • Testing the impact of metabolic inhibitors and sulfhydryl reagents on the observed stimulation.
  • Comparing the characteristics of the membrane redox cycle with ascorbate uptake.

    • Main Results:

    • Catalytic amounts of ascorbate or dehydroascorbate significantly stimulated transmembrane oxidant reduction by K562 and U937 cells.
    • The stimulation was not mediated by the transport of ascorbate in different redox states into or out of the cells.
    • The membrane redox cycle demonstrated high affinity for ascorbate and linear kinetics, requiring the presence of cells.
    • Metabolic inhibitors and sulfhydryl reagents effectively inhibited the stimulated reduction.
    • Ascorbate uptake was observed but exhibited different kinetics and much lower affinity, suggesting it's a separate process.

    Conclusions:

    • K562 and U937 leukemic cells possess a membrane-associated redox cycle that utilizes ascorbate to reduce extracellular oxidants.
    • This process is distinct from ascorbate uptake and is sensitive to metabolic inhibition, indicating an enzymatic component.
    • The findings suggest a novel mechanism for leukemic cells to modulate their redox environment.