scholarly journals Effect of micromolar concentrations of manganese ions on calcium-ion cycling in rat liver mitochondria

1983 ◽  
Vol 212 (3) ◽  
pp. 773-782 ◽  
Author(s):  
B P Hughes ◽  
J H Exton
Keyword(s):  
Rat Liver ◽  
Calcium Ion ◽  
Incubation Medium ◽  
Liver Mitochondria ◽  
Ruthenium Red ◽  
Rat Liver Mitochondria ◽  
Manganese Ions ◽  
Dose Dependent Decrease ◽  
Incubation Temperatures ◽  
Dose Dependent

The effects of micromolar concentrations of Mn2+ on the rat liver mitochondrial Ca2+ cycle were investigated. It was found that the addition of Mn2+ to mitochondria which were cycling 45Ca2+ led to a rapid dose dependent decrease in the concentration of extramitochondrial 45Ca2+ of about 1 nmol/mg of protein. The effect was complete within 30 s, was half maximal with 10 microM Mn2+ and was observed in the presence of 3 mM Mg2+ and 1 mM ATP. It occurred over a broad range of incubation temperatures, pH and mitochondrial Ca2+ loads. It was not observed when either Mg2+ or phosphate was absent from the incubation medium, or in the presence of Ruthenium Red. These findings indicate that micromolar concentrations of Mn2+ stimulate the uptake of Ca2+ by rat liver mitochondria, and provide evidence for an interaction between Mg2+ and Mn2+ in the control of mitochondrial Ca2+ cycling.

scholarly journals Calcium ion cycling in rat liver mitochondria

1978 ◽  
Vol 174 (2) ◽  
pp. 613-620 ◽  
Author(s):  
Chidambaram Ramachandran ◽  
Fyfe L. Bygrave
Keyword(s):  
Rat Liver ◽  
Calcium Ion ◽  
Mitochondrial Membrane ◽  
Initial Rate ◽  
Liver Mitochondria ◽  
Ruthenium Red ◽  
Rat Liver Mitochondria ◽  
Inner Mitochondrial Membrane ◽  
Subsequent Addition ◽  
Unique Mechanism

1. Addition of N-ethylmaleimide to rat liver mitochondria respiring with succinate as substrate decreases both the initial rate of Ca2+ transport and the ability of mitochondria to retain Ca2+. As a result, Ca2+ begins to leave the mitochondria soon after it has entered. Half-maximal effects occur at an N-ethylmaleimide concentration of about 100nmol/mg of protein. 2. The efflux of Ca2+ induced by N-ethylmaleimide is not prevented by Mg2+ or by Ruthenium Red at concentrations known to prevent Ca2+ efflux when exogenous phosphate also is present. Swelling of mitochondria does not accompany N-ethylmaleimide-induced Ca2+ efflux. 3. Addition of Ca2+ to rat liver mitochondria in the presence of N-ethylmaleimide produces an immediate decrease in ΔE (membrane potential), which decreases further to only a slight extent over the next 8min. Concomitant with this is an immediate increase and then levelling off of the −59ΔpH (transmembrane pH gradient). 4. Preincubation of rat liver mitochondria with p-chloromercuribenzenesulphonate, which by contrast with N-ethylmaleimide is unable to penetrate the inner mitochondrial membrane, also prevents Ca2+ retention. The ΔE and −59ΔpH respond to Ca2+ addition in a manner similar to that which occurs when N-ethylmaleimide is present. Subsequent addition of mercaptoethanol produces an immediate increase in both ΔE and −59ΔpH. At the same time Ca2+ is rapidly accumulated by the organelles. 5. The above data are interpreted as indicating that under the conditions of Ca2+ efflux seen here, the mitochondria retain their functional integrity. This contrasts with the uncoupling effect of Ca2+ seen in the presence of Pi, which generally leads to a loss of mitochondrial integrity. We suggest that a unique mechanism of Ca2+ cycling is able to take place when mitochondria have been treated with N-ethylmaleimide.

Mechanism of sodium ion independent calcium ion efflux from rat liver mitochondria

Biochemistry ◽  
1983 ◽  
Vol 22 (26) ◽  
pp. 6341-6351 ◽  
Author(s):  
T. E. Gunter ◽  
J. H. Chace ◽  
J. S. Puskin ◽  
K. K. Gunter
Keyword(s):  
Rat Liver ◽  
Calcium Ion ◽  
Liver Mitochondria ◽  
Sodium Ion ◽  
Rat Liver Mitochondria ◽  
Ion Efflux

Pathway for uncoupler-induced calcium efflux in rat liver mitochondria: inhibition by Ruthenium Red

Biochemistry ◽  
1984 ◽  
Vol 23 (8) ◽  
pp. 1645-1651 ◽  
Author(s):  
Paolo Bernardi ◽  
Venturina Paradisi ◽  
Tullio Pozzan ◽  
Giovanni Felice Azzone
Keyword(s):  
Rat Liver ◽  
Liver Mitochondria ◽  
Ruthenium Red ◽  
Rat Liver Mitochondria ◽  
Calcium Efflux

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.

scholarly journals Stimulation of the respiration rate of rat liver mitochondria by sub-micromolar concentrations of extramitochondrial Ca2+

1987 ◽  
Vol 245 (1) ◽  
pp. 217-222 ◽  
Author(s):  
J D Johnston ◽  
M D Brand
Keyword(s):  
Respiration Rate ◽  
Rat Liver ◽  
Oxidative Metabolism ◽  
Mitochondrial Respiration ◽  
Liver Mitochondria ◽  
Ruthenium Red ◽  
Rat Liver Mitochondria ◽  
Mitochondrial Matrix ◽  
Stimulation Of

1. The respiration rate of rat liver mitochondria was stimulated by up to 70% when the extramitochondrial Ca2+ concentration was raised from 103 to 820 nM. This occurred when pyruvate, 2-oxoglutarate, or threo-(Ds)-isocitrate was employed as substrate, but not when succinate was used. 2. Ruthenium Red prevented the stimulation of mitochondrial respiration by extramitochondrial Ca2+, showing that the effect required Ca2+ uptake into the mitochondrial matrix. 3. Starvation of rats for 48 h abolished the stimulation of mitochondrial respiration by extramitochondrial Ca2+ when pyruvate was used as substrate, but did not affect the stimulation of 2-oxoglutarate oxidation by extramitochondrial Ca2+. 4. Our findings are in accord with proposals that oxidative metabolism in liver mitochondria may be stimulated by Ca2+ activation of intramitochondrial dehydrogenases.

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