scholarly journals The purified and reconstituted ornithine/citrulline carrier from rat liver mitochondria catalyses a second transport mode: ornithine+/H+ exchange

1999 ◽  
Vol 341 (3) ◽  
pp. 705-711 ◽  
Author(s):  
Cesare INDIVERI ◽  
Annamaria TONAZZI ◽  
Italo STIPANI ◽  
Ferdinando PALMIERI
Keyword(s):  
Rat Liver ◽  
Opposite Direction ◽  
Incubation Medium ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Ph Indicator ◽  
Transport Mode ◽  
Essential Step ◽  
Opposite Compartment

The mechanism of unidirectional transport of ornithine (i.e. in the absence of a counter-metabolite) has been investigated in proteoliposomes reconstituted with the ornithine carrier purified from rat liver mitochondria. The efflux of [3H]ornithine from proteoliposomes was stimulated by the addition of H+ (but not of other cations) to the incubation medium . On keeping the pH in the compartment containing ornithine constant at 8.0, the flux of ornithine into or out of the proteoliposomes increased on decreasing the pH in the opposite compartment from 8.0 to 6.0. Ornithine influx was also stimulated when a higher H+ concentration was generated inside the vesicles relative to the outside by the K+/H+ exchanger nigericin in the presence of an outwardly directed K+ gradient. A valinomycin-induced electrogenic flux of K+ did not affect ornithine transport in the absence of a counter-metabolite. Furthermore, changes in fluorescence of the pH indicator pyranine, included inside the proteoliposomes, showed that the flux of ornithine is accompanied by translocation of H+ in the opposite direction. It is concluded that the mitochondrial ornithine carrier catalyses an electroneutral exchange of ornithine+ for H+, in addition to the well-known 1:1 exchange of metabolites. Lysine+, but not citrulline, can also be exchanged for H+ by the ornithine carrier. The ornithine+/H+ transport mode of the exchanger is an essential step in the catabolism of excess arginine.

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 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 Studies on the efflux of metalloporphyrin from rat liver mitochondria. Effect of K+ and other cations

1981 ◽  
Vol 196 (2) ◽  
pp. 451-457 ◽  
Author(s):  
P Husby ◽  
I Romslo
Keyword(s):  
Ionic Strength ◽  
Rat Liver ◽  
Incubation Medium ◽  
Energy State ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Isolated Rat Liver ◽  
Sucrose Medium ◽  
Low Ionic Strength ◽  
Isolated Rat

The mechanism by which metalloporphyrins synthesized within the mitochondria escape to the incubation medium was studied in isolated rat liver mitochondria. In a low-ionic-strength sucrose medium, the efflux of metalloporphyrins is markedly decreased when K+ (greater than 10 mM) is added. The effect of K+ is not dependent on the energy state of the mitochondria and it can in part be abolished by adding globin, but not albumin. K+ also decreases the uptake of porphyrins by the mitochondria and thereby the rate of synthesis of metalloporphyrins. Qualitatively similar results are found with Na+, Li+, Mg2+ and Ca2+. Quantitatively, however, the efficiency of cations to inhibit the release of metalloporphyrins decreases in the order: Mg2+ greater than Ca2+ greater than K+ greater than Li+ greater than Na+. Co-protoporhyrin behaves essentially as Co-deuteroporphyrin. The results provide further evidence that the efflux of metalloporphyrins from the mitochondria depends on haem-binding ligands of the suspending medium and also on the ionic strength of the incubation medium.

scholarly journals The purified and reconstituted ornithine/citrulline carrier from rat liver mitochondria: electrical nature and coupling of the exchange reaction with H+ translocation

1997 ◽  
Vol 327 (2) ◽  
pp. 349-356 ◽  
Author(s):  
Cesare INDIVERI ◽  
Annamaria TONAZZI ◽  
Italo STIPANI ◽  
Ferdinando PALMIERI
Keyword(s):  
Exchange Rates ◽  
Exchange Reaction ◽  
Rat Liver ◽  
Transport Process ◽  
Liver Mitochondria ◽  
The Other ◽  
Rat Liver Mitochondria ◽  
Ph Indicator ◽  
External Ph ◽  
Reasonable Model

The mechanism and the electrical nature of ornithine/citrulline exchange has been investigated in proteoliposomes reconstituted with the ornithine/citrulline carrier purified from rat liver mitochondria. The stoichiometry of the exchanging substrates was close to 1:1. The exchange was not affected by inducing electrogenic flux of K+ with valinomycin. In contrast, the pH gradient generated by the K+/H+ exchanger nigericin in the presence of an outwardly directed K+ gradient stimulated the ornithineout/citrullinein exchange, but not the ornithine/ornithine homoexchange. Experiments in which either the internal or the external pH was varied, while keeping constant the pH in the other compartment, indicated that maximal exchange rates are found at pH 6 in the compartment containing citrulline and at pH 8 in the compartment containing ornithine. Changes in fluorescence of the pH indicator pyranine, included inside the proteoliposomes, showed that the exchanges ornithineout/citrullinein and citrullineout/ornithinein are accompanied by translocation of H+ in the same direction as citrulline. It is concluded that the mitochondrial ornithine/citrulline carrier catalyses an electroneutral exchange of ornithine+ for citrulline plus an H+. A reasonable model is one in which ornithine binds to a deprotonated carrier and citrulline to a protonated carrier and both substrate-carrier complexes are neutral. The physiological implications of this transport process are discussed.

Influence of Ionic Strength of Incubation Medium on the Release of Some Enzymes from Rat Liver Mitochondria

Enzyme ◽  
1975 ◽  
Vol 19 (5-6) ◽  
pp. 337-347 ◽  
Author(s):  
L.F. Panchenko ◽  
T.D. Loktaeva ◽  
A.M. Gerasimov
Keyword(s):  
Ionic Strength ◽  
Rat Liver ◽  
Incubation Medium ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria

scholarly journals Studies on the efflux of metalloporphyrin from rat-liver mitochondria. Effect of albumin, globin, haemin and haemoglobin

1980 ◽  
Vol 188 (2) ◽  
pp. 459-465 ◽  
Author(s):  
P Husby ◽  
I Romslo
Keyword(s):  
Steady State ◽  
Rat Liver ◽  
Incubation Medium ◽  
Model Compound ◽  
Energy State ◽  
Energy Coupling ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Isolated Rat Liver ◽  
Isolated Rat

The mechanism by which metalloporphyrins escape from mitochondria has been studied in isolated rat-liver mitochondria using Co-deuteroporphyrin as the model compound. During the first 10–15 min of incubation the efflux is about 10% of the total amount of Co-deuteroporphyrin synthesized. The efflux then increases to a second steady-state leve of 25–35% after 30–45 min of incubation. The efflux is inversely correlated to the energy state of the mitochondria. Globin at concentrations less than 0.4 mumol/l enhances the efflux of Co-deuteroporphyrin, but has no effect on the degree of energy coupling or on the rate of Co-deuteroporphyrin synthesis. The effect of globin can be competitively inhibited by adding haemin. Haemin (0.5–1.0 mumol/l) when added to the medium in the absence of globin reduces the efflux of Co-deuteroporphyrin by 20–30%, but has no effect on the metal-chelatase activity. Neither albumin nor haemoglobin increases the efflux of Co-deuteroporphyrin from intact mitochondria. The results suggest that the efflux of metalloporphyrin is regulated in part by the energy state of the mitochondria and in part by the presence of metalloporphyrin-binding ligants and unattached haemin in the incubation medium.

Effects of 5-5'-Diphenyl-2-thiohydantoin (DPTH) and Thyroxine on the Ultrastructure and Chemical Composition of Rat Liver

1971 ◽  
Vol 29 ◽  
pp. 570-571
Author(s):  
E. A. Elfont ◽  
R. B. Tobin ◽  
D. G. Colton ◽  
M. A. Mehlman
Keyword(s):  
Chemical Composition ◽  
Rat Liver ◽  
Future Study ◽  
Mode Of Action ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Effective Inhibitor ◽  
Biochemical Effects ◽  
Glycerophosphate Dehydrogenase ◽  
Stimulation Of

Summary5,-5'-diphenyl-2-thiohydantoin (DPTH) is an effective inhibitor of thyroxine (T4) stimulation of α-glycerophosphate dehydrogenase in rat liver mitochondria. Because this finding indicated a possible tool for future study of the mode of action of thyroxine, the ultrastructural and biochemical effects of DPTH and/or thyroxine on rat liver mere investigated.Rats were fed either standard or DPTH (0.06%) diet for 30 days before T4 (250 ug/kg/day) was injected. Injection of T4 occurred daily for 10 days prior to sacrifice. After removal of the liver and kidneys, part of the tissue was frozen at -50°C for later biocheailcal analyses, while the rest was prefixed in buffered 3.5X glutaraldehyde (390 mOs) and post-fixed in buffered 1Z OsO4 (376 mOs). Tissues were embedded in Araldlte 502 and the sections examined in a Zeiss EM 9S.Hepatocytes from hyperthyroid rats (Fig. 2) demonstrated enlarged and more numerous mitochondria than those of controls (Fig. 1). Glycogen was almost totally absent from the cytoplasm of the T4-treated rats.

Energy and Antioxidant Status of Rat Liver Mitochondria during Hypoxia- Reoxygenation of Different Duration

2016 ◽  
Vol 7 (4) ◽  
pp. 349-361
Author(s):  
Olga A. Gonchar ◽  
Valentina I. Nosar ◽  
Larisa. V. Bratus ◽  
I. N. Tymchenko ◽  
N. N. Steshenko ◽  
...  
Keyword(s):  
Rat Liver ◽  
Antioxidant Status ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Hypoxia Reoxygenation
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