HETEROGENEITY AND DIFFERENTIAL FRAGILITY OF RAT LIVER MITOCHONDRIA

1966 ◽  
Vol 44 (5) ◽  
pp. 497-508 ◽  
Author(s):  
C. V. Lusena ◽  
Florent Depocas
Keyword(s):  
Rat Liver ◽  
High Speed ◽  
Specific Activity ◽  
Mitochondrial Protein ◽  
Total Activity ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Fraction I

Five fractions (I–V) of intact mitochondria were obtained from rat liver by differential centrifugation during isolation. They represented respectively 4, 9, 64, 11, and 11% of the total mitochondrial protein. No striking differences between mitochondria sedimented at low speed (fraction I) and those sedimented at high speed (fraction V) were seen by electron microscopy. In all samples glutamic dehydrogenase (GD) specific activity was the same after deoxycholate treatment and less than 1% of the total activity could be detected in the fresh fractions. Overnight freezing at −5 °C of fractions I, III, and V followed by thawing at 37 °C liberated 25, 11, and 6% respectively of the total GD activity. The greater fragility of fraction I relative to that of fraction V was also apparent in the phase-contrast microscope during warming to room temperature; lysis occurred in 10 minutes in fraction I and in 1 hour in fraction V. The distribution of GD activity after centrifugation on sucrose density gradients indicated that partial disruption of the mitochondria had occurred in decreasing degree from fractions I to V. The different fragilities of the fractions in vitro did not reflect different lability in vivo since all fractions had the same rates of turnover as measured after they were labeled with14C acetate. The results are discussed in terms of heterogeneities observed by other methods.

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 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.

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