Plasma membrane potential

Fat Increased glucose transport GLUT4-translocation PI 3-kinase/Akt mediated translocation of GLUT4 into the plasma membrane. Potential involvement of atypical forms of protein kinase C (PKC and A)... 

De Nicola, M. et al. (2008) Carbon nanotubes on Jurkat cells effects on cell viability and plasma membrane potential. Journal of Physics Condensed Matter,... 

Tab. 5.8 Plasma membrane potentials in PDR cell lines3. (Reprinted from Tab. 1 of ref. 95 with permission from Bertelsmann-Springer) ...

Moule, S.K. McGivan, J.D. (1990). Regulation of the plasma membrane potential in hepatocytes— mechanism and physiological significance. Biochim. Biophys. Acta 1031,383-397. 

C. Suppose that, when the cell is placed in the d ark, the influx and the efflux both become 0.1 nmol m 2 s-1. If the plasma membrane potential is —118 mV (inside negative) and the same concentration occurs on the two sides of the membrane, what can be said about the energetics of the two fluxes ... 

Information is also encoded within the frequency of Ca + oscillations that occur in the cytosol. Oscillations can derive either from fluctuations of the entry of external calcium or of the release from internal stores. The former occur primarily in excitable cells, after the periodic opening of plasma membrane Ca + channels, such as induced, for example, by the rhythmic changes of the plasma membrane potential of the heart or by bursts of action potential in neurons. In nonexcitable cells, the predominant mechanism of [Ca +]c elevation is from the activation of plasma membrane receptors coupled to G-proteins... 

Increases of intracellular free Ca concentratirm that are initiated by changes in plasma membrane potential or receptcH -stimulated polyphosphoinositide (Pis) hydrolysis are astonishingly complex. The key to understanc g these complex Ca signals lies in undmtanding the interactions betweoi different cellular pools fi om whidi Ca rapidly enters the cytosol and their transporting systems (74-76). These cellular events are summarized in Figure 3. 

ExtraceHuiar calcium provides calcium ion for the maintenance of intracellular calcium, bone mineralization, blood coagulation, and plasma membrane potential. Calcium stabilizes the plasma membranes and influences permeability and excitability. A decrease in the serum free calcium concentration causes increased neuromuscular excitability and tetany an increased concentration reduces neuromuscular excitability. 

Arvan P, Kim PS, Kuliawat R, et al. Intracellular protein transport to the thyrocyte plasma membrane Potential implications for thyroid physiology. Thyroid 1997 7 89-105. 

The membrane potential of individual cells can be monitored with a fluorescence microscope. For this purpose, however, it is preferable to use a permeable redistribution dye with spectral characteristics that have minimal environmental sensitivity. Thus, the fluorescence intensity will reflect the degree of Nemstian accumulation of dye only and can, therefore, be readily interpreted. The plasma membrane potential can be distinguished from the organelle membrane by simply using the microscope to identify appropriate regions of the cell (44). Rhodamine-123 (Chart III) was introduced as a mitochondrial stain by Chen and co-workers (45-47) it has been used largely in qualitative studies of mitochondrial membrane potential and has been especially effective in flow cytometry applications. 

Piwnica-Worms D, Kronauge JF and Chiu ML. Uptake and retention of hexakis (2-methoxyisobutyl isonitrile) technetium(I) in cultured chick myocardial cells. Mitochondrial and plasma membrane potential dependence. Circulation 1990 82 1826 1838. 

Chiu ML, Kronauge JF and Piwnica-Worms D. Effect of mitochondrial and plasma membrane potentials on accumulation of hexakis (2-methoxyisobutylisonitrile) techne-tium(I) in cultured mouse fibroblasts. J Nucl Med 1990 31 1646-1653. 

Chemical uncouplers can also influence cell fate other than through depletion of ATP [153, 154] and their action to depolarize membranes outside of the mitochondrion also needs to be considered with respect to their overall effects on the target cell or organism for instance, they have been shown to dissipate plasma membrane potential and to destabilize lyzosomes [155, 156]. 

Figure 5. Compound VGP-318 does not alter the plasma membrane potential in Leishmania lines. Promastigotes were incubated with 30 pM of compound VGP-318 for 3 h and then treated with 2 pM of the specific plasma membrane potential probe D1BAC4(3) for 10 min at 28 Untreated parasites were used as control, and treatment with 10 pM CCCP was used as 100% depolarization of the plasma membrane potential. Data are means SD of three independent e)q eriments. Significant differences were determined using Student s f-test p< 0.01).

Chromophores which are non-toxic at low concentrations may become potent inhibitors if they are concentrated in specific compartments. Cyanine dyes severely inhibit respiration at site 1 of the mitochondrial respiratory chain, providing that the inner mitochondrial membrane potential is substantial (inside negative) (18). In living cells, the irmer mitochondrial membrane potential is about 180 mV and the plasma membrane potential is about 60 mV (both inside negative), and extracellular csranine at 10" m is at electrochemical eqrrilibrium with mitochondrial cyanine when the latter reaches 10 m. Very low concentrations of cyanines may thus adversely affect cellular respiration and energy dependent processes (18). 

Plasma membrane potential of animal cells The membrane potential of whole cells is more difficult to assess than that of isolated organelles with optical indicators because cells contain many sub-ccllular compartments, and it is necessary to isolate the response of the plasma membrane from that of any other cell membrane. For example, the intense staining of mitochondria by cyanine dyes (7). which are membrane-permeant cations, means that if you choose a cyanine dye, or other lipophilic cation, lo measure plasma membrane potential it is important to establish conditions where the mitochondrial potential is disabled. If an anionic dye is chosen, this problem is overcome but there is, then, very little entry of dye into the cells unless the dye is itself reasonably lipophilic. Thus, for studies of whole cells, we employ an oxonol dye with a phenyl substituent. The procedures fijr mc.isuring plasma membrane potential with this dye, oxonol-V (31), are illustrated in R,giirf. j and Protocol 2. 

Measurement of plasma membrane potential using oxonol-V and cells In suspension... 

About 80% of the energy produced in the brain is consumed by neurons, which constitute only 10% of all brain cells. Such large amounts of energy are indispensable for the maintenance and restoration of neuronal plasma membrane potentials (of several Hz frequency) during events linked to neurotransmission. 

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