scholarly journals A membrane potential-modulated pathway for Ca2+ efflux in rat liver mitochondria

FEBS Letters ◽  
1982 ◽  
Vol 139 (1) ◽  
pp. 13-16 ◽  
Author(s):  
Paolo Bernardi ◽  
Giovanni Felice Azzone
Keyword(s):  
Membrane Potential ◽  
Rat Liver ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria

scholarly journals Studies on the efflux of metalloporphyrin from isolated rat liver mitochondria. Effect of respiratory substrates and metabolic inhibitors

1982 ◽  
Vol 202 (1) ◽  
pp. 41-46 ◽  
Author(s):  
P Husby ◽  
I Romslo
Keyword(s):  
Membrane Potential ◽  
Rat Liver ◽  
Incubation Medium ◽  
Energy State ◽  
Liver Mitochondria ◽  
Metabolic Inhibitors ◽  
Rat Liver Mitochondria ◽  
Isolated Rat Liver ◽  
Isolated Rat

Intramitochondrially synthesized Co-deuteroporphyrin is released to the incubation medium at a rate inversely correlated to the energy state of the mitochondria; i.e. the rate of efflux increases when substrate is depleted, respiration inhibited or the mitochondria are uncoupled. The efflux of Co-deuteroporphyrin from mitochondria remains low as long as the residual membrane potential is above one-third that of maximally energized mitochondria. Globin enhances the efflux of Co-deuteroporphyrin not only from mitochondria depleted of substrates [Husby & Romslo (1980) Biochem. J. 188, 459-465], but also from maximally energized mitochondria. The results provide further evidence for a co-operative mechanism between the mitochondria and their surroundings for the mobilization of metalloporphyrin from mitochondria.

Accumulation of D-arginine by rat liver mitochondria

1987 ◽  
Vol 65 (12) ◽  
pp. 1057-1063 ◽  
Author(s):  
Rafael Villalobos-Molina ◽  
J. Pablo Pardo ◽  
Alfredo Saavedra-Molina ◽  
Enrique Piña
Keyword(s):  
Membrane Potential ◽  
Rat Liver ◽  
Mitochondrial Respiration ◽  
Mitochondrial Membrane ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Inner Mitochondrial Membrane ◽  
Osmotic Swelling ◽  
Dose Dependent Fashion ◽  
Dose Dependent

The permeability of the inner mitochondrial membrane from rat liver to D-arginine was studied. By using safranin as a probe of the membrane potential, depolarization of energized liver mitochondria occurred in a dose-dependent fashion starting at 3.3 mmol/L of D- or DL-arginine. When ethidium bromide fluorescence was employed, a decrease in the membrane potential due to D- or DL-arginine was observed. A parallel significant change in succinate-induced respiration in rat liver mitochondria was found in response to osmotic swelling in 125 mmol/L of D-arginine salts. L-Arginine, L-glutamine, L-asparagine, L-ornithine, D-ornithine, and L-lysine did not modify the membrane potential at the concentrations tested. D-Arginine was not transformed into citrulline, but 1.0 mmol/L of the D-amino acid inhibited, by 42%, the state 3 of mitochondrial respiration using succinate as substrate. When D-arginine was used in combination with nigericin, a 40% inhibition of mitochondrial respiration in state 3 was recorded with succinate and with glutamate–malate as substrates.

scholarly journals The regulation of extramitochondrial free calcium ion concentration by rat liver mitochondria

1978 ◽  
Vol 176 (2) ◽  
pp. 463-474 ◽  
Author(s):  
David G. Nicholls
Keyword(s):  
Steady State ◽  
Membrane Potential ◽  
Rat Liver ◽  
Liver Mitochondria ◽  
Weak Acid ◽  
Ion Concentration ◽  
Rat Liver Mitochondria ◽  
Free Calcium ◽  
Electrochemical Gradient

The mechanism whereby rat liver mitochondria regulate the extramitochondrial concentration of free Ca2+ was investigated. At 30°C and pH7.0, mitochondria can maintain a steady-state pCa2+0 (the negative logarithm of the free extramitochondrial Ca2+ concentration) of 6.1 (0.8μm). This represents a true steady state, as slight displacements in pCa2+0 away from 6.1 result in net Ca2+ uptake or efflux in order to restore pCa2+0 to its original value. In the absence of added permeant weak acid, the steady-state pCa2+0 is virtually independent of the Ca2+ accumulated in the matrix until 60nmol of Ca2+/mg of protein has been taken up. The steady-state pCa2+0 is also independent of the membrane potential, as long as the latter parameter is above a critical value. When the membrane potential is below this value, pCa2+0 is variable and appears to be governed by thermodynamic equilibration of Ca2+ across a Ca2+ uniport. Permeant weak acids increase, and N-ethylmaleimide decreases, the capacity of mitochondria to buffer pCa2+0 in the region of 6 (1μm-free Ca2+) while accumulating Ca2+. Permeant acids delay the build-up of the transmembrane pH gradient as Ca2+ is accumulated, and consequently delay the fall in membrane potential to values insufficient to maintain a pCa2+0 of 6. The steady-state pCa2+0 is affected by temperature, incubation pH and Mg2+. The activity of the Ca2+ uniport, rather than that of the respiratory chain, is rate-limiting when pCa2+0 is greater than 5.3 (free Ca2+ less than 5μm). When the Ca2+ electrochemical gradient is in excess, the activity of the uniport decreases by 2-fold for every 0.12 increase in pCa2+0 (fall in free Ca2+). At pCa2+0 6.1, the activity of the Ca2+ uniport is kinetically limited to 5nmol of Ca2+/min per mg of protein, even when the Ca2+ electrochemical gradient is large. A steady-state cycling of Ca2+ through independent influx and efflux pathways provides a model which is kinetically and thermodynamically consistent with the present observations, and which predicts an extremely precise regulation of pCa2+0 by liver mitochondria in vivo.

scholarly journals T-2307 Causes Collapse of Mitochondrial Membrane Potential in Yeast

2012 ◽  
Vol 56 (11) ◽  
pp. 5892-5897 ◽  
Author(s):  
Tatsuya Shibata ◽  
Toshinari Takahashi ◽  
Eio Yamada ◽  
Akiko Kimura ◽  
Hiroshi Nishikawa ◽  
...  
Keyword(s):  
Membrane Potential ◽  
Mitochondrial Membrane Potential ◽  
Rat Liver ◽  
Mitochondrial Function ◽  
Mitochondrial Membrane ◽  
Liver Mitochondria ◽  
Yeast Cells ◽  
Rat Liver Mitochondria ◽  
Content Type ◽  
Glycerol Medium

ABSTRACTT-2307, an arylamidine compound, has been previously reported to have broad-spectrumin vitroandin vivoantifungal activities against clinically significant pathogens, includingCandidaspecies,Cryptococcus neoformans, andAspergillusspecies, and is now undergoing clinical trials. Here we investigated the mechanism of action of T-2307 using yeast cells and mitochondria isolated from yeast and rat liver. Nonfermentative growth ofCandida albicansandSaccharomyces cerevisiaein glycerol medium, in which yeasts relied on mitochondrial respiratory function, was inhibited at 0.001 to 0.002 μg/ml (0.002 to 0.004 μM) of T-2307. However, fermentative growth in dextrose medium was not inhibited by T-2307. Microscopic examination using Mitotracker fluorescent dye, a cell-permeant mitochondrion-specific probe, demonstrated that T-2307 impaired the mitochondrial function ofC. albicansandS. cerevisiaeat concentrations near the MIC in glycerol medium. T-2307 collapsed the mitochondrial membrane potential in mitochondria isolated fromS. cerevisiaeat 20 μM. On the other hand, in isolated rat liver mitochondria, T-2307 did not have any effect on the mitochondrial membrane potential at 10 mM. Moreover, T-2307 had little inhibitory and stimulatory effect on mitochondrial respiration in rat liver mitochondria. In conclusion, T-2307 selectively disrupted yeast mitochondrial function, and it was also demonstrated that the fungal mitochondrion is an attractive antifungal target.

scholarly journals The nature of the calcium ion efflux induced in rat liver mitochondria by the oxidation of endogenous nicotinamide nucleotides

1980 ◽  
Vol 188 (1) ◽  
pp. 113-118 ◽  
Author(s):  
D G Nicholls ◽  
M D Brand
Keyword(s):  
Membrane Potential ◽  
Rat Liver ◽  
Calcium Ion ◽  
Respiratory Control ◽  
Liver Mitochondria ◽  
Critical Value ◽  
Mitochondrial Damage ◽  
Rat Liver Mitochondria ◽  
Ion Efflux ◽  
Complete Collapse

Ca2+ efflux from rat liver mitochondria can occur when endogenous nicotinamide nucleotides are oxidized. It is suggested that nicotinamide nucleotide induced by acetoacetate sensitizes the mitochondria to damaage resulting from the accumulation of Ca2+ in the presence of Pi. Thus, acetoacetate-induced Ca2+ efflux is associated with a loss of respiratory control. Both the effluxes induced by acetoacetate and by high Ca2+ accumulation are prevented by ATP plus oligomycin, although these agents do not prevent the endoagenous nicotinamide nucleotides from becoming oxidized on addition of acetoacetate. Acetoacetate addition only results in Ca2+ release if the Ca2+ and Pi concentration are above a critical value. The acetoacetate-induced Ca2+ effflux is exactly paralled by the virtually complete collapse of the membrane potential. The presence of acetoacetate decreases the concentration of total Ca2+ necessary to induced mitochondrial damage by about 130 nmol of Ca2+/mg of protein. It is concluded that acetoacetate-induced efflux occurs by reversal of the Ca2+ uniporter after the collapse of the membrane potential.

Sign in / Sign up

Export Citation Format

Share Document