scholarly journals Selective permeability of rat liver mitochondria to purified aspartate aminotransferases in vitro

1977 ◽  
Vol 164 (3) ◽  
pp. 685-691 ◽  
Author(s):  
E Marra ◽  
S Doonan ◽  
C Saccone ◽  
E Quagliariello
Keyword(s):  
Rat Liver ◽  
Aspartate Aminotransferase ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Transferase Activity ◽  
Selective Permeability ◽  
The Matrix ◽  
Mitochondrial Aspartate Aminotransferase

1. A method was devised to allow determination of intramitochondrial aspartate amino-transferase activity in suspensions of intact mitochondria. 2. Addition of purified rat liver mitochondrial aspartate aminotransferase to suspensions of rat liver mitochondria caused an apparent increase in the intramitochondrial enzyme activity. No increase was observed when the mitochondria were preincubated with the purified cytoplasmic isoenzyme. 3. These results suggest that mitochondrial aspartate aminotransferase, but not the cytoplasmic isoenzyme, is able to pass from solution into the matrix of intact rat liver mitochondria in vitro. 4. This system may provide a model for studies of the little-understood processes by which cytoplasmically synthesized components are incorporated into mitochondria in vivo.

Import of the glucocorticoid receptor into rat liver mitochondria in vivo and in vitro

1993 ◽  
Vol 46 (3) ◽  
pp. 401-413 ◽  
Author(s):  
C. Demonacos ◽  
N.C. Tsawdaroglou ◽  
R. Djordjevic-Markovic ◽  
M. Papalopoulou ◽  
V. Galanopoulos ◽  
...  
Keyword(s):  
Glucocorticoid Receptor ◽  
Rat Liver ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria

scholarly journals Stable enhancement of calcium retention in mitochondria isolated from rat liver after the administration of glucagon to the intact animal

1978 ◽  
Vol 176 (3) ◽  
pp. 705-714 ◽  
Author(s):  
Veronica Prpić ◽  
Terry L. Spencer ◽  
Fyfe L. Bygrave
Keyword(s):  
Rat Liver ◽  
Molecular Mechanisms ◽  
Adenine Nucleotide ◽  
Adenine Nucleotides ◽  
Mitochondrial Protein ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Matrix Space ◽  
The Matrix

1. Mitochondria isolated from rat liver by centrifugation of the homogenate in buffered iso-osmotic sucrose at between 4000 and 8000g-min, 1h after the administration in vivo of 30μg of glucagon/100g body wt., retain Ca2+ for over 45min after its addition at 100nmol/mg of mitochondrial protein in the presence of 2mm-Pi. In similar experiments, but after the administration of saline (0.9% NaCl) in place of glucagon, Ca2+ is retained for 6–8min. The ability of glucagon to enhance Ca2+ retention is completely prevented by co-administration of 4.2mg of puromycin/100g body wt. 2. The resting rate of respiration after Ca2+ accumulation by mitochondria from glucagon-treated rats remains low by contrast with that from saline-treated rats. Respiration in the latter mitochondria increased markedly after the Ca2+ accumulation, reflecting the uncoupling action of the ion. 3. Concomitant with the enhanced retention of Ca2+ and low rates of resting respiration by mitochondria from glucagon-treated rats was an increased ability to retain endogenous adenine nucleotides. 4. An investigation of properties of mitochondria known to influence Ca2+ transport revealed a significantly higher concentration of adenine nucleotides but not of Pi in those from glucagon-treated rats. The membrane potential remained unchanged, but the transmembrane pH gradient increased by approx. 10mV, indicating increased alkalinity of the matrix space. 5. Depletion of endogenous adenine nucleotides by Pi treatment in mitochondria from both glucagon-treated and saline-treated rats led to a marked diminution in ability to retain Ca2+. The activity of the adenine nucleotide translocase was unaffected by glucagon treatment of rats in vivo. 6. Although the data are consistent with the argument that the Ca2+-translocation cycle in rat liver mitochondria is a target for glucagon action in vivo, they do not permit conclusions to be drawn about the molecular mechanisms involved in the glucagon-induced alteration to this cycle.

scholarly journals Selective permeability of rat liver mitochondria to purified malate dehydrogenase isoenzymes in vitro

1980 ◽  
Vol 192 (2) ◽  
pp. 649-658 ◽  
Author(s):  
S Passarella ◽  
E Marra ◽  
S Doonan ◽  
E Quagliariello
Keyword(s):  
Malate Dehydrogenase ◽  
Rat Liver ◽  
Liver Mitochondria ◽  
Enzymic Activity ◽  
Rat Liver Mitochondria ◽  
Starch Gel Electrophoresis ◽  
Selective Permeability ◽  
Starch Gel ◽  
Mitochondrial Malate Dehydrogenase

1. The mitochondrial malate dehydrogenase from rat liver has been purified to a state of homogeneity as judged by starch-gel electrophoresis and the cytoplasmic isoenzyme has been obtained in a partically purified state. 2. Inhibition of the isoenzymes by sulphite has been studied. 3. In mitochondria loaded with sulphite, the catalytic activity of the (partially inhibited) internal malate dehydrogenase has been measured by addition of oxaloacetate to the suspension medium and observation of the consequent decrease in fluorescence of NADH. 4. Addition of mitochondrial malate dehydrogenase to suspensions of mitochondria loaded with sulphite resulted in an increase in the level of intramitochondrial enzymic activity as measured by the above technique. Addition of the cytoplasmic isoenzyme did not result in such an increase. 5. These results show that mitochondria in suspension are permeable to the mitochondrial malate dehydrogenase but not to the cytoplasmic isoenzyme. 6. This conclusion has been confirmed by direct measurement of a decrease of enzyme activity in solution and an increase inside the mitochondria after incubation of organelles in solutions containing mitochondrial malate dehydrogenase. No such effect was observed with the cytoplasmic isoenzyme. 7. Some features of the permeation process have been studied.

scholarly journals d-Lactate transport and metabolism in rat liver mitochondria

2002 ◽  
Vol 365 (2) ◽  
pp. 391-403 ◽  
Author(s):  
Lidia de BARI ◽  
Anna ATLANTE ◽  
Nicoletta GUARAGNELLA ◽  
Giovanni PRINCIPATO ◽  
Salvatore PASSARELLA
Keyword(s):  
Lactate Dehydrogenase ◽  
Rat Liver ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Lactate Metabolism ◽  
Inner Membrane ◽  
Mitochondrial Inner Membrane ◽  
The Matrix ◽  
Inside Out

In the present study we investigated whether isolated rat liver mitochondria can take up and metabolize d-lactate. We found the following: (1) externally added d-lactate causes oxygen uptake by mitochondria [P/O ratio (the ratio of mol of ATP synthesized to mol of oxygen atoms reduced to water during oxidative phosphorylation) = 2] and membrane potential (Δψ) generation in processes that are rotenone-insensitive, but inhibited by antimycin A and cyanide, and proton release from coupled mitochondria inhibited by α-cyanocinnamate, but not by phenylsuccinate; (2) the activity of the putative flavoprotein (d-lactate dehydrogenase) was detected in inside-out submitochondrial particles, but not in mitochondria and mitoplasts, as it is localized in the matrix phase of the mitochondrial inner membrane; (3) three novel separate translocators exist to mediate d-lactate traffic across the mitochondrial inner membrane: the d-lactate/H+ symporter, which was investigated by measuring fluorimetrically the rate of endogenous flavin reduction, the d-lactate/oxoacid antiporter (which mediates both the d-lactate/pyruvate and d-lactate/oxaloacetate exchanges) and d-lactate/malate antiporter studied by monitoring photometrically the appearance of the d-lactate counteranions outside mitochondria. The d-lactate translocators, in the light of their different inhibition profiles separate from the monocarboxylate carrier, were found to differ from each other in the Vmax values and in the inhibition and pH profiles and were shown to regulate mitochondrial d-lactate metabolism in vitro. The d-lactate translocators and the d-lactate dehydrogenase could account for the removal of the toxic methylglyoxal from cytosol, as well as for d-lactate-dependent gluconeogenesis.

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