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Oxygen Consumption Rates and Oxygen Concentration in Molt-4 Cells and Their mtDNA Depleted (⁰) Mutants

Jiangang Shen^*, Nadeem Khan^*, Lionel D. Lewis, Ray Armand, Oleg Grinberg^*, Eugene Demidenko and Harold Swartz^*

^* EPR Center, Department of Diagnostic Radiology, Dartmouth Medical School, Hanover, New Hampshire 03755 USA; Section of Clinical Pharmacology, Department of Medicine, Dartmouth-Hitchcock Medical Center, Lebanon, New Hampshire 03756 USA; and Section of Biostatistics and Epidemiology, Dartmouth Medical School, Hanover, New Hampshire 03755 USA

Correspondence: Address reprint requests to Harold M. Swartz, EPR Center, Dept. of Diagnostic Radiology, 7785 Vail, Room 702, Dartmouth Medical School, Hanover, NH 03755 USA. Tel.: 603-650-1955; Fax: 603-650-1717; E-mail: Harold.Swartz{at}dartmouth.edu.

Respiratory deficient cell lines are being increasingly used to elucidate the role of mitochondria and to understand the pathophysiology of mitochondrial genetic disease. We have investigated the oxygen consumption rates and oxygen concentration in wild-type (WT) and mitochondrial DNA (mtDNA) depleted (⁰) Molt-4 cells. Wild-type Molt-4 cells have moderate oxygen consumption rates, which were significantly reduced in the ⁰ cells. PCMB (p-chloromercurobenzoate) inhibited the oxygen consumption rates in both WT and ⁰ cells, whereas potassium cyanide decreased the oxygen consumption rates only in WT Molt-4 cells. Menadione sodium bisulfite (MSB) increased the oxygen consumption rates in both cell lines, whereas CCCP (carbonyl cyanide m-chlorophenylhydrazone) stimulated the oxygen consumption rates only in WT Molt-4 cells. Superoxide radical adducts were observed in both WT and ⁰ cells when stimulated with MSB. The formation of this adduct was inhibited by PCMB but not by potassium cyanide. These results suggest that the reactive oxygen species (ROS) induced by MSB were at least in part produced via a mitochondrial independent pathway. An oxygen gradient between the extra- and intracellular compartments was observed in WT Molt-4 cells, which further increased when cells were stimulated by CCCP and MSB. The results are consistent with our earlier findings suggesting that such oxygen gradients may be a general phenomenon found in most or all cell systems under appropriate conditions.

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