scholarly journals Effects of glucagon and N6O2′-dibutyryladenosine 3′:5′-cyclic monophosphate on calcium transport in isolated rat liver mitochondria

1978 ◽  
Vol 176 (1) ◽  
pp. 295-304 ◽  
Author(s):  
B P Hughes ◽  
G J Barritt
Keyword(s):  
Retention Time ◽  
Calcium Transport ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Dibutyryl Cyclic Amp ◽  
Oxygen Utilization ◽  
Isolated Rat Liver ◽  
Isolated Mitochondria ◽  
Isolated Liver ◽  
Stimulation Of

1. The administration of glucagon to fed rats by intraperitoneal injection, or the perfusion of livers from fed rats with glucagon by the method of Mortimore [Mortimore (1963) Am.J. Physiol. 204, 699–704] was associated with increases of 15- and 5-fold respectively, in the time for which a given load of exogenous Ca2+ is retained by mitochondria subsequently isolated from the liver. This effect of glucagon was (a) also induced by N6O2′-dibutyryl cyclic AMP, (b) completely blocked by cycloheximide, (c) relatively slow in onset (15–60 min) and (d) associated with a stimulation of about 20% in the rates of ADP-stimulated oxygen utilization and Ca2+ transport measured in the presence of succinate. 2. Perfusion of livers with glucagon resulted in the isolation of mitochandria which showed a 50% increase, no significant change and a 40% increase in the concentrations of endogenous Ca, Mg and Pi respectively, when compared with mitochondria isolated from control perfused livers. 3. The administration of insulin or adrenaline to fed rats induced increases of 10- and 8-fold respectively, in the time for which Ca2+ is retained by isolated liver mitochondria. Perfusion of livers with insulin had no effect on mitochondrial Ca2+ retention time. 4. The perfusion of livers from starved rats with glucagon, or the administration of either glucagon or insulin to starved rats, increased by about 2.5- and 15-fold respectively, the time for which isolated mitochondria retain Ca2+. 5. Mechanisms which may be responsible for the observed alterations in Ca2+-retention time are discussed.

scholarly journals Protein-mediated uptake of vitamin B12 by isolated mitochondria

Blood ◽  
1976 ◽  
Vol 47 (6) ◽  
pp. 923-930 ◽  
Author(s):  
RA Gams ◽  
EM Ryel ◽  
F Ostroy
Keyword(s):  
Vitamin B12 ◽  
Rat Liver ◽  
Mitochondrial Respiration ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Isolated Rat Liver ◽  
Isolated Mitochondria ◽  
Isolated Rat

Abstract Protein-mediated B12 uptake by isolated rat liver mitochondria has been shown to be enhanced by plasma transcobalamin (TC-II) but not by salivary R binder in vitro. The process is enhanced by calcium and depends on active mitochondrial respiration. Following uptake, cyanocobalamin is converted to adenosyl and methylcobalamins and released from the mitochondria. TC-II appears to be required for both cellular and mitochondrial uptake of vitamin B12.

scholarly journals Evidence for β-adrenergic activation of Na+-dependent efflux of Ca2+ from isolated liver mitochondria

1982 ◽  
Vol 204 (1) ◽  
pp. 369-371 ◽  
Author(s):  
Timothy P. Goldstone ◽  
Martin Crompton
Keyword(s):  
Rat Liver ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Adrenergic Agonist ◽  
Isolated Rat Liver ◽  
Dependent Activity ◽  
Adrenergic Activation ◽  
Isolated Liver ◽  
Isolated Rat ◽  
Dependent Mechanism

The existence of a Na+-dependent mechanism for Ca2+ efflux from isolated rat liver mitochondria was confirmed. The activity of this system is decreased by 60% in mitochondria isolated from perfused livers. The Na+-dependent activity is fully restored by infusion of either 1μm-adrenaline or 1μm-isoprenaline, but the α-adrenergic agonist phenylephrine is ineffective.

scholarly journals Protein-mediated uptake of vitamin B12 by isolated mitochondria

Blood ◽  
1976 ◽  
Vol 47 (6) ◽  
pp. 923-930
Author(s):  
RA Gams ◽  
EM Ryel ◽  
F Ostroy
Keyword(s):  
Vitamin B12 ◽  
Rat Liver ◽  
Mitochondrial Respiration ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Isolated Rat Liver ◽  
Isolated Mitochondria ◽  
Isolated Rat

Protein-mediated B12 uptake by isolated rat liver mitochondria has been shown to be enhanced by plasma transcobalamin (TC-II) but not by salivary R binder in vitro. The process is enhanced by calcium and depends on active mitochondrial respiration. Following uptake, cyanocobalamin is converted to adenosyl and methylcobalamins and released from the mitochondria. TC-II appears to be required for both cellular and mitochondrial uptake of vitamin B12.

scholarly journals Osmotic behavior and permeability of osmotically lysed mitochondria.

1976 ◽  
Vol 70 (2) ◽  
pp. 348-357 ◽  
Author(s):  
C L Bowman ◽  
H Tedeschi ◽  
B J DiDomenico ◽  
F D Tung
Keyword(s):  
External Medium ◽  
Volume Ratio ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Isolated Rat Liver ◽  
Virtual Absence ◽  
Isolated Mitochondria ◽  
Cell Biol ◽  
Molecular Components ◽  
Osmotic Behavior

Experiments were carried out with water-treated isolated rat liver mitochondria (mitochondria ghosts) previously studied by Caplan and Greenawalt (Caplan, A.I., and J.W. Greenawalt. 1966. J. Cell Biol. 31:455-472) and Vasington and Greenawalt (Vasington, F., and J. Greenawalt. 1968. J. Cell Biol. 39:661-675). The ghosts have permeability properties and osmotic behavior comparable to those of isolated mitochondria. Although they have lost most of their internal contents, they must have resealed. Four properties were found which have not been previously described in systems derived from biological membranes: (a) an osmotic behavior in the virtual absence of internal components. (b) a self-arranging property in the formation of invaginations corresponding in morphology to the cristae. The results suggest that the assembly of the molecular components of the inner membrane is sufficient to specify the morphology. Hence the surface area to volume ratio of the vesicles may specify the presence or absence of cristae-like folds. (c) an increase in the permeability of the membranes to sucrose in the presence of iso-osmotic concentrations of sucrose. (d) an independence of the light transmitted by suspensions of the vesicles from the refractive index of the external medium. This observations run counter to the general previous experience with either mitochondria or liposomes.

scholarly journals Factors influencing the activity of ornithine aminotransferase in isolated rat liver mitochondria

1977 ◽  
Vol 162 (1) ◽  
pp. 147-156 ◽  
Author(s):  
J D McGivan ◽  
N M Bradford ◽  
A D Beavis
Keyword(s):  
Mitochondrial Membrane ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Ornithine Aminotransferase ◽  
Aminotransferase Activity ◽  
Exchange System ◽  
Isolated Rat Liver ◽  
Isolated Mitochondria ◽  
Factors Influencing ◽  
Kinetics Of

1. The characteristics of ornithine catabolism by the aminotransferase pathway in isolated mitochondria were determined. 2. Ornithine synthesis from glutamate and glutamate gamma-semialdehyde produced by the oxidation of proline was studied. No ornithine was formed in the absence of rotenone. 3. The mechanism of ornithine transport was reinvestigated, and the existence of an ornithine+/H+ exchange system postulated. 4. The kinetics of ornithine transport, ornithine catabolism in intact mitochondria and ornithine aminotransferase activity in solubilized mitochondria were compared. It is concluded that ornithine aminotransferase activity in liver mitochondria is rate-limited by the transport of ornithine across the mitochondrial membrane, and that this enzyme is involved primarily in ornithine degradation rather than ornithine synthesis.

scholarly journals Oxaloacetate- and acetoacetate-induced calcium efflux from mitochondria occurs by reversal of the uptake pathway

1982 ◽  
Vol 202 (1) ◽  
pp. 197-201 ◽  
Author(s):  
M E Bardsley ◽  
M D Brand
Keyword(s):  
Membrane Potential ◽  
Mitochondrial Membrane ◽  
Liver Mitochondria ◽  
Ruthenium Red ◽  
Rat Liver Mitochondria ◽  
Calcium Efflux ◽  
Isolated Rat Liver ◽  
Uptake Pathway ◽  
Mitochondrial Integrity ◽  
Stimulation Of

1. Addition of oxaloacetate or acetoacetate to isolated rat liver mitochondria results in an efflux of Ca2+. Concomitant with this efflux is an immediate oxidation of endogenous nicotinamide nucleotides, a fall in the mitochondrial membrane potential and an increase in the rate of respiration. The primary effect in this sequence may be either (a) physiologically important stimulation of a Ca2+-efflux carrier, followed by Ca2+ re-uptake, a fall in membrane potential and increased respiration, or (b) physiologically unimportant damage to mitochondrial integrity, followed by a fall in membrane potential, increased respiration and Ca2+ efflux. 2. Ruthenium Red and EGTA will restore the increased respiratory rate to one approximating to the control rate of respiration. However, addition of lanthanide, at a concentration which inhibits the uptake but not the normal efflux of Ca2+, inhibits the rate of Ca2+ efflux induced by oxaloacetate or acetoacetate. Therefore the observed efflux is occurring by a reversal of the uptake pathway (uniporter) and thus follows the fall in membrane potential. 3. From these results we conclude that the decrease in membrane potential and increase in the rate of respiration seen during oxaloacetate- or acetoacetate-induced Ca2+ efflux cannot be accounted for by rapid Ca2+ cycling, but are due to damage to mitochondrial integrity.

scholarly journals ANGULAR LIGHT-SCATTERING STUDIES ON ISOLATED MITOCHONDRIA

1961 ◽  
Vol 10 (1) ◽  
pp. 15-21 ◽  
Author(s):  
Gerald S. Gotterer ◽  
Thomas E. Thompson ◽  
Albert L. Lehninger
Keyword(s):  
Light Scattering ◽  
Optical Density ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Density Measurements ◽  
Isolated Rat Liver ◽  
Isolated Mitochondria ◽  
Large Particles ◽  
Scattering Measurements ◽  
Increased Sensitivity

Angular light-scattering studies have been carried out on suspensions of isolated rat liver mitochondria. The angular scatter pattern has a large forward component, typical of large particles. Changes in dissymmetry and in the intensity of light scattered at 90° have been correlated with changes in optical density during the course of mitochondrial swelling and contraction. Such changes can be measured at mitochondrial concentrations much below those required for optical density measurements. Changes in mitochondrial geometry caused by factors "leaking" from mitochondria, not detectable by optical density measurements, have been demonstrated by measuring changes in dissymmetry. Angular light-scattering measurements therefore offer the advantages of increased sensitivity and of added indices of changes in mitochondrial conformation.

scholarly journals Interaction between glucocorticoids and glucagon in the hormonal modification of calcium retention by isolated rat liver mitochondria

1979 ◽  
Vol 180 (2) ◽  
pp. 291-295 ◽  
Author(s):  
B P Hughes ◽  
G J Barritt
Keyword(s):  
Retention Time ◽  
Fold Increase ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Isolated Rat Liver ◽  
Calcium Retention ◽  
Full Effect ◽  
New Protein ◽  
Isolated Rat ◽  
Adrenalectomized Rats

1. The administration of dexamethasone to intact fed rats by intraperitoneal injection for 3h was associated with a 6-fold increase in the time for which mitochondria subsequently isolated from the liver retain a given load of exogenous Ca2+. This effect was blocked by the co-administration of cycloheximide with dexamethasone, and partially blocked by the co-administration of puromycin. Daily administration of dexamethasone for periods of 4–7 days resulted in liver mitochondria that exhibited a decreased ability to retain exogenous Ca2+. 2. When glucagon was administered to fed adrenalectomized rats, the increase in mitochondrial Ca2+-retention time that results from the action of this hormone was reduced by 50% when compared with its effect on intact animals. The administration of dexamethasone to adrenalectomized rats partially restored the full effect of glucagon. 3. Dexamethasone did not enhance the effect of glucagon on mitochondrial Ca2+-retention time when administered to intact fed rats. 4. It is concluded that these data support the hypothesis that the hormone-induced modification of liver mitochondria, which results in an increase in the time for which exogenous Ca2+ is retained, involves a step in which new protein is synthesized.

scholarly journals Effect of l-leucine on the nitrogen metabolism of isolated rat liver mitochondria

1973 ◽  
Vol 134 (1) ◽  
pp. 209-215 ◽  
Author(s):  
J. D. McGivan ◽  
Norah M. Bradford ◽  
M. Crompton ◽  
J. B. Chappell
Keyword(s):  
Glutamate Dehydrogenase ◽  
Nitrogen Metabolism ◽  
Mitochondrial Membrane ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Isolated Rat Liver ◽  
Isolated Mitochondria ◽  
Citrulline Synthesis ◽  
Glutamate Synthesis ◽  
Rate Limiting

1. l-Leucine strongly activated intramitochondrial glutamate dehydrogenase in the direction of glutamate synthesis. 2. In the deamination direction, the enzyme was not stimulated by leucine. This was probably due to a rate-limiting transport of glutamate across the mitochondrial membrane. 3. The effect of leucine on the kinetic constants of glutamate dehydrogenase in a mitochondrial sonicate was studied. 4. In isolated mitochondria, leucine did not stimulate the synthesis of citrulline with glutamate as the source of NH3. 5. Leucine very markedly stimulated the synthesis of glutamate from added 2-oxoglutarate+NH4Cl. 6. Under conditions where glutamate and citrulline could be synthesized simultaneously from added NH4Cl, leucine greatly increased glutamate synthesis at the expense of citrulline synthesis. 7. It is suggested that the intramitochondrial leucine concentration may be a factor influencing the nitrogen metabolism of the liver cell.

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