THE OXIDIZING-AGENT MENADIONE INDUCES AN INCREASE IN THE INTRACELLULAR MOLECULAR-OXYGEN CONCENTRATION IN K562 AND A431 CELLS - DIRECT MEASUREMENT USING NEW PARAMAGNETIC EPR PROBE FUSINITE

The intracellular molecular oxygen concentration in control and menadi one-treated K562 (an erythroleukemic cell line that grows in suspensio n) and A431 (an epidermal carcinoma that grows in monolayer) cells was measured directly by using the new electron paramagnetic resonance (E PR) probe fusinite. Because the oxidizing agent menadione is known to damage mitochondria and the cytoplasmic membrane in other cell systems , before conducting measurements of oxygen concentration in K562 and A 431 cells, it was necessary to establish injury in these systems as we ll. Consequently, morphological and flow cytometric analyses were cond ucted after menadione treatment. The data presented here show that the two cell lines are heavily damaged by menadione. Once this menadione- induced injury was demonstrated, measurements of oxygen concentration were carried out in both K562 and A431 cells. Treatment with this quin one induces a sharp increase in intracytoplasmic molecular oxygen in b oth cell lines (from about 1% to about 10 and 15% in K562 and A431 cel ls, respectively). In addition, to gain a more complete understanding of the effects of menadione on cells, the extracellular molecular oxyg en concentration and the oxygen consumption rate were also measured in control and menadione-treated K562 cells. These measurements demonstr ate that menadione treatment results in an increase in the extracellul ar oxygen concentration (from about 5% in controls to 15% in treated c ells) as well as a decrease in the oxygen consumption rate (from about 10 ng O/min/10(6) cells in controls to 3 ng O/min/10(6) cells after m enadione exposure). The importance of the new EPR probe fusinite in mo nitoring directly cellular functions in which oxygen is involved and t he effects of menadione on cellular oxygen balance are discussed.