Mitochondrial membrane potential regulation is independent of c-fos expression

1999 ◽  
Vol 77 (3) ◽  
pp. 195-203
Author(s):  
Roger A Moorehead ◽  
Gurmit Singh
Keyword(s):  
Membrane Potential ◽  
Ovarian Carcinoma ◽  
Mitochondrial Membrane Potential ◽  
Mitochondrial Membrane ◽  
Membrane Potentials ◽  
Rhodamine 123 ◽  
Parental Line ◽  
Rat Fibroblasts ◽  
Human Ovarian Carcinoma ◽  
Fos Expression

Tumour cells contain mitochondria with elevated membrane potentials compared with normal cells, and thus this feature provides a selective target for destroying tumour cells. To improve mitochondrial-based therapies, a better understanding of the factors involved in regulating mitochondria are required. Since v-fos overexpression has been shown to elevate mitochondrial membrane potentials in rat fibroblasts, we investigated whether the human homologue, c-fos, was also capable of regulating the mitochondrial membrane potential in cells. Rat fibroblasts transfected with the c-fos gene did not accumulate more rhodamine 123 (Rh123) nor did they retain this Rh123 for extended periods of time compared with their parental line. Moreover, there was no difference in survival following dequalinium chloride (Deca) treatment between transfectants and controls. Similarly, reduction of c-fos expression in rat fibroblasts did not significantly alter their mitochondrial membrane potential. In addition, human ovarian carcinoma cells, which overexpress the c-fos gene, did not accumulate more Rh123 nor were they hypersensitive to Deca compared with their parental line. In another human ovarian carcinoma cell line, selection of variants with lower mitochondrial membrane potential did not alter c-fos mRNA or protein levels. These data suggest that alterations in c-fos expression do not regulate the magnitude of the mitochondrial membrane potential.Key words: c-fos, mitochondria, membrane potential, rhodamine 123 (Rh123), lipophilic cations.

scholarly journals Energy transduction in intact synaptosomes. Influence of plasma-membrane depolarization on the respiration and membrane potential of internal mitochondria determined in situ

1980 ◽  
Vol 186 (1) ◽  
pp. 21-33 ◽  
Author(s):  
I D Scott ◽  
D G Nicholls
Keyword(s):  
Plasma Membrane ◽  
Membrane Potential ◽  
Mitochondrial Membrane Potential ◽  
Mitochondrial Membrane ◽  
Significant Proportion ◽  
Membrane Potentials ◽  
Simultaneous Estimation ◽  
Anaerobic Glycolysis ◽  
Mitochondrial Potential ◽  
Plasma Membrane Potential

A method is described, based on the differential accumulation of Rb+ and methyltriphenylphosphonium, for the simultaneous estimation of the membrane potentials across the plasma membrane of isolated nerve endings (synaptosomes), and across the inner membrane of mitochondria within the synaptosomal cytoplasm. These determinations, together with measurements of respiratory rates, and ATP and phosphocreatine concentrations, are used to define the bioenergetic behaviour of isolated synaptosomes under a variety of conditions. Under control conditions, in the presence of glucose, the plasma and mitochondrial membrane potentials are respectively 45 and 148mV. Addition of a proton translocator induces a 5-fold increase in respiration, and abolishes the mitochondrial membrane potential. The addition of rotenone to inhibit respiration does not affect the plasma membrane potential, and only lowers the mitochondrial membrane potential to 128mV. Evidence is presented that ATP synthesis by anaerobic glycolysis is sufficient under these conditions to maintain ATP-dependent processes, including the reversal of the mitochondrial ATP synthetase. Addition of oligomycin under non-respiring conditions leads to a complete collapse of the mitochondrial potential. Even under control conditions the plasma membrane (Na+ + K+)-dependent ATPase is responsible for a significant proportion of the synaptosomal ATP turnover. Veratridine greatly increases respiration, and depolarizes the plasma membrane, but only slightly lowers the mitochondrial membrane potential. High K+ and ouabain also lower the plasma membrane potential without decreasing the mitochondrial membrane potential. In non-respiring synaptosomes, anaerobic glycolysis is incapable of maintaining cytosolic ATP during the increased turnover induced by veratridine, and the mitochondrial membrane potential collapses. It is concluded that the internal mitochondria must be considered in any study of synaptosomal transport.

scholarly journals Rise in cytosolic Ca2+ and collapse of mitochondrial potential in anoxic, but not hypoxic, rat proximal tubules.

1996 ◽  
Vol 7 (11) ◽  
pp. 2348-2356
Author(s):  
S M Peters ◽  
M J Tijsen ◽  
R J Bindels ◽  
C H Van Os ◽  
J F Wetzels
Keyword(s):  
Membrane Potential ◽  
Mitochondrial Membrane Potential ◽  
Mitochondrial Membrane ◽  
Cell Injury ◽  
Cell Damage ◽  
Energy State ◽  
Oxygen Deprivation ◽  
Proximal Tubules ◽  
Rhodamine 123 ◽  
Anoxic Conditions

It has been suggested that ischemic renal proximal tubular cell injury is mediated by an increase in cytosolic calcium concentrations ((Ca2+)i). However, measurements of (Ca2+)i in rat or rabbit proximal tubules exposed to hypoxia or anoxia have yielded ambiguous results. This study explored the possibility that the severity of oxygen deprivation and the energy state of the mitochondria are important determinants of (Ca2+)i. To this end, (Ca2+)i (measured with fura-2) and the mitochondrial membrane potential (measured with rhodamine 123) were studied simultaneously in individual rat proximal tubules in hypoxic and anoxic conditions. (Ca2+)i did not change during hypoxia, but increased rapidly during anoxia. Increases in (Ca2+)i were only observed in parallel with a decrease of rhodamine 123 fluorescence, which indicates a collapse of the mitochondrial membrane potential. The increase in (Ca2+)i during anoxia was prevented by incubating the tubules in a low Ca2+ medium, which did not interfere with the collapse of the mitochondrial membrane potential. Both hypoxic and anoxic incubation led to cell death, as assessed by the fluorescent dye propidium iodide. These results clearly demonstrate that the level of oxygen deprivation is critical in determining changes in (Ca2+)i. Because cell damage occurred in both hypoxic and anoxic conditions. It was concluded that an increase in (Ca2+)i is not a necessary prerequisite for the development of ischemic cell injury.

scholarly journals A membrane-activatable near-infrared fluorescent probe with ultra-photostability for mitochondrial membrane potentials

The Analyst ◽  
2016 ◽  
Vol 141 (12) ◽  
pp. 3679-3685 ◽  
Author(s):  
Wei Ren ◽  
Ao Ji ◽  
Omran Karmach ◽  
David G. Carter ◽  
Manuela M. Martins-Green ◽  
...  
Keyword(s):  
Membrane Potential ◽  
Fluorescent Probe ◽  
Mitochondrial Membrane Potential ◽  
Mitochondrial Membrane ◽  
Near Infrared ◽  
Living Cells ◽  
Membrane Potentials ◽  
Fluorescence Quencher

Dark for light: A fluorescence quencher was turned into a near-infrared probe for mitochondrial membrane potential in living cells and mice.

scholarly journals Is the Mitochondrial Membrane Potential (∆Ψ) Correctly Assessed? Intracellular and Intramitochondrial Modifications of the ∆Ψ Probe, Rhodamine 123

2022 ◽  
Vol 23 (1) ◽  
pp. 482
Author(s):  
Ljubava D. Zorova ◽  
Evgeniya A. Demchenko ◽  
Galina A. Korshunova ◽  
Vadim N. Tashlitsky ◽  
Savva D. Zorov ◽  
...  
Keyword(s):  
Membrane Potential ◽  
Mitochondrial Membrane Potential ◽  
Mitochondrial Membrane ◽  
Fluorescent Microscopy ◽  
Rhodamine 123 ◽  
Proton Pumps ◽  
Hydrogen Ions ◽  
Mandatory Requirement ◽  
Electrical Component

The mitochondrial membrane potential (∆Ψ) is the driving force providing the electrical component of the total transmembrane potential of hydrogen ions generated by proton pumps, which is utilized by the ATP synthase. The role of ∆Ψ is not limited to its role in bioenergetics since it takes part in other important intracellular processes, which leads to the mandatory requirement of the homeostasis of ∆Ψ. Conventionally, ∆Ψ in living cells is estimated by the fluorescence of probes such as rhodamine 123, tetramethylrodamine, etc. However, when assessing the fluorescence, the possibility of the intracellular/intramitochondrial modification of the rhodamine molecule is not taken into account. Such changes were revealed in this work, in which a comparison of normal (astrocytic) and tumor (glioma) cells was conducted. Fluorescent microscopy, flow cytometry, and mass spectrometry revealed significant modifications of rhodamine molecules developing over time, which were prevented by amiodarone apparently due to blocking the release of xenobiotics from the cell and their transformation with the participation of cytochrome P450. Obviously, an important role in these processes is played by the increased retention of rhodamines in tumor cells. Our data require careful evaluation of mitochondrial ∆Ψ potential based on the assessment of the fluorescence of the mitochondrial probe.

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