scholarly journals Transport and oxidation of choline by liver mitochondria

1977 ◽  
Vol 166 (3) ◽  
pp. 571-581 ◽  
Author(s):  
D. D. Tyler
Keyword(s):  
Mitochondrial Membrane ◽  
Adenine Nucleotides ◽  
Close Correlation ◽  
Liver Mitochondria ◽  
Mitochondrial Swelling ◽  
Ionophore A23187 ◽  
Phospholipase Activity ◽  
Choline Transport ◽  
Tightly Coupled

1. Rapid choline oxidation and the onset of Pi-induced swelling by liver mitochondria, incubated in a sucrose medium at or above pH7.0, required the addition of both Pi and an uncoupling agent. Below pH7.0, Pi alone was required for rapid choline oxidation and swelling. 2. Choline oxidation was inhibited by each of several reagents that also inhibited Pi-induced swelling under similar conditions of incubation, including EGTA, mersalyl, Mg2+, the Ca2+-ionophore A23187, rotenone and nupercaine. None of these reagents had any significant effect on the rate of choline oxidation by sonicated mitochondria. There was therefore a close correlation between the conditions required for rapid choline oxidation and for Pi-induced swelling to occur, suggesting that in the absence of mitochondrial swelling the rate of choline oxidation is regulated by the rate of choline transport across the mitochondrial membrane. 3. Respiratory-chain inhibitors, uncoupling agents (at pH6.5) and ionophore A23187 caused a loss of endogenous Ca2+ from mitochondria, whereas nupercaine and Mg2+ had no significant effect on the Ca2+ content. Inhibition of choline oxidation and mitochondrial swelling by ionophore A23187 was reversed by adding Ca2+, but not by Mg2+. It is concluded that added Pi promotes the Ca2+-dependent activation of mitochondrial membrane phospholipase activity in respiring mitochondria, causing an increase in the permeability of the mitochondrial inner membrane to choline and therefore enabling rapid choline oxidation to occur. Nupercaine and Mg2+ appear to block choline oxidation and swelling by inhibiting phospholipase activity. 4. Choline was oxidized slowly by tightly coupled mitochondria largely depleted of their endogenous adenine nucleotides, suggesting that these compounds are not directly concerned in the regulation of choline oxidation. 5. The results are discussed in relation to the possible mechanism of choline transport across the mitochondrial membrane in vivo and the influence of this process on the pathways of choline metabolism in the liver.

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 Inorganic pyrophosphate is located primarily in the mitochondria of the hepatocyte and increases in parallel with the decrease in light-scattering induced by gluconeogenic hormones, butyrate and ionophore A23187

1988 ◽  
Vol 254 (2) ◽  
pp. 379-384 ◽  
Author(s):  
A M Davidson ◽  
A P Halestrap
Keyword(s):  
Light Scattering ◽  
Adenine Nucleotides ◽  
Hormone Treatment ◽  
Subcellular Fractionation ◽  
Liver Mitochondria ◽  
Cell Protein ◽  
Ionophore A23187 ◽  
Inorganic Pyrophosphate ◽  
Rat Liver Cells ◽  
The Mean

1. The effects of a variety of hormones on the PPi content and light-scattering of isolated rat liver cells was studied. 2. The basal PPi content was about 130 pmol/mg of cell protein, and increased after hormone addition, in parallel with a decrease in light-scattering which we have observed previously [Quinlan, Thomas, Armston & Halestrap (1983) Biochem. J. 214, 395-404]. 3. The mean increases in PPi content with the agonists shown (as pmol/mg of protein) were: 0.1 microM-glucagon, 25; 20 microM-phenylephrine, 30; 25 nM-vasopressin, 127; glucagon + phenylephrine, 115; glucagon + vasopressin, 382; 100 microM-ADP, 50; 15 microM-A23187, 72; 1 mM-butyrate, 80. 4. In the absence of extracellular Ca2+, vasopressin had little effect on either the PPi content or the light-scattering of hepatocytes. 5. The magnitude of the increase in PPi content correlated with that of the decrease in light-scattering irrespective of the stimulating agent, provided that the PPi did not exceed 300 pmol/mg of protein. Above this value little additional change in light-scattering was observed. 6. Subcellular fractionation showed that over 90% of the cellular PPi was intramitochondrial in both control and stimulated cells. 7. The data support the conclusions of previous experiments using isolated liver mitochondria [Davidson & Halestrap (1987) Biochem. J. 246, 715-723] that hormones increase the mitochondrial matrix volume through a Ca2+-induced rise in matrix [PPi]. 8. It is further proposed that this increase in mitochondrial [PPi] allows entry of ADP into the mitochondria in exchange for PPi and is therefore responsible for the increase in total mitochondrial adenine nucleotides observed after hormone treatment.

Hepatotrophic effects of insulin on glucose, glycogen, and adenine nucleotides in hepatocytes isolated from fed adult rats

1980 ◽  
Vol 58 (10) ◽  
pp. 1004-1011 ◽  
Author(s):  
Khursheed N. Jeejeebhoy ◽  
Joseph Ho ◽  
Rajni Mehra ◽  
Alan Bruce-Robertson
Keyword(s):  
Adenine Nucleotide ◽  
Adenine Nucleotides ◽  
Energy Charge ◽  
Close Correlation ◽  
Adult Rats ◽  
Fed State ◽  
Adenine Nucleotide Pool ◽  
Intracellular Glucose

In vivo observations have suggested that there is an hepatotrophic effect of insulin. By contrast, subsequent in vitro work, using the isolated perfused liver system, showed no effect or indeterminate effects of insulin on the transport of glucose into the hepatocyte. However because this system may not have endured long enough to show such an influence we explored the transport of glucose using a 48-h suspension culture of hepatocytes isolated from young adult fed rats, the suspension being infused continuously with insulin at a rate approximating the maximum entering portal blood in the fed state. (In a separate study phloridzin was added after 2 h of incubation.) DNA, intracellular glucose and its inward transport, glycogen, and the adenine nucleotides were measured at intervals. By comparison with control or untreated cells, insulin-treated cells showed significantly more DNA and intracellular glucose, and the differences were abolished by phloridzin. Glucose transport rates fell to low values in untreated controls and still lower with insulin plus phloridzin. but the initial rate was maintained to the end (48 h) by insulin alone. Results for glycogen were similar to those for intracellular glucose. There was a close correlation (r = 0.96) between these two. The total adenine nucleotide pool and the concentration of ATP were maintained for about 24 h and fell to half their initial values by 48 h. Insulin had increased these concentrations significantly by 6 h. Although concentrations of ADP and AMP decreased gradually in all groups of cells, insulin enhanced the level of ADP by 12 h but had no measurable effect on that of AMP. The energy charge increased slightly throughout incubation but more so (by 6 h) in the presence of insulin. In conclusion the data support the concept that in the longer term (> 12 h) insulin in the portal circulation maintains the characteristic free permeability of the hepatocyte to glucose and this permits a variety of effects related to glucose entry into the hepatocyte.

Hepatoprotection of Oleanolic Acid is Related to Its Inhibition on Mitochondrial Permeability Transition

2005 ◽  
Vol 33 (04) ◽  
pp. 627-637 ◽  
Author(s):  
Xin-Hui Tang ◽  
Jing Gao ◽  
Feng Fang ◽  
Jin Chen ◽  
Li-Zhi Xu ◽  
...  
Keyword(s):  
Membrane Potential ◽  
Mitochondrial Membrane Potential ◽  
Oleanolic Acid ◽  
Mitochondrial Membrane ◽  
Permeability Transition ◽  
Liver Mitochondria ◽  
Mitochondrial Swelling ◽  
Dependent Manner ◽  
Protective Effects ◽  
Mitochondrial Membrane Depolarization

The protective effects of oleanolic acid (OA) on carbon tetrachloride (CCl4)-induced liver mitochondrial damage and the possible mechanisms were investigated. Pretreatment with OA prior to the administration of CCl4 significantly suppressed the increases of serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) (4.2- and 19.9-fold, respectively) in a dose-dependent manner in mice. The dissipation of mitochondrial membrane potential (14.8%) and intra-mitochondrial Ca 2+ overload (2.1-fold) in livers of CCl4-insulted mice were also dose-dependently prevented by pretreatment with 20, 50 or 100 mg/kg OA. In addition, the effects of OA on liver mitochondria permeability transition (MPT) induced by Ca 2+ were assessed by measuring the change in mitochondrial membrane potential, release of matrix Ca 2+ and mitochondrial swelling in vitro. The results showed that preincubation with 50 or 100 μg/ml OA obviously inhibited the Ca 2+-induced mitochondrial swelling, mitochondrial membrane depolarization and intra-mitochondrial Ca 2+ release. It could be concluded that OA has protective effects on liver mitochondria and the mechanisms underlying its protection may be related to its inhibitory action on MPT.

scholarly journals The transport and accumulation of adenine nucleotides during mitochondrial biogenesis

1980 ◽  
Vol 192 (1) ◽  
pp. 75-83 ◽  
Author(s):  
J K Pollak ◽  
R Sutton
Keyword(s):  
Rat Liver ◽  
Adenine Nucleotide ◽  
Adenine Nucleotides ◽  
Liver Mitochondria ◽  
Adenine Nucleotide Translocase ◽  
Luciferase Assay ◽  
Rat Liver Mitochondria ◽  
Matrix Space ◽  
Foetal Rat

The atractyloside-insensitive accumulation of adenine nucleotides by rat liver mitochondria (as opposed to the exchange-diffusion catalysed by the adenine nucleotide translocase) has been measured by using the luciferin/luciferase assay as well as by measuring [14C]ATP uptake. In foetal rat liver mitochondria ATP is accumulated more rapidly than ADP, whereas AMP is not taken up. The uptake of ATP occurs against a concentration gradient, and the rate of ATP uptake is greater in foetal than in adult rat liver mitochondria. The accumulated [14C]ATP is shown to be present within the mitochondrial matrix space and is freely available to the adenine nucleotide translocase for exchange with ATP present in the external medium. The uptake is specific for ATP and ADP and is not inhibited by adenosine 5′-[beta gamma-imido] triphosphate, GTP, CTP, cyclic AMP or Pi, whereas dATP and AMP do inhibit ATP accumulation. The ATP accumulation is also inhibited by carbonyl cyanide m-chlorophenylhydrazone, KCN and mersalyl but is insensitive to atractyloside. The ATP uptake is concentration-dependent and exhibits Michaelis-Menten kinetics. The divalent cations Mg2+ and Ca2+ greatly enhance ATP accumulation, and the presence of hexokinase inhibits the uptake of ATP by foetal rat liver mitochondria. These latter effects provide an explanation for the low adenine nucleotide content of foetal rat liver mitochondria and the rapid increase that occurs in the mitochondrial adenine nucleotide concentration in vivo immediately after birth.

scholarly journals Regulation of the mitochondrial matrix volume in vivo and in vitro. The role of calcium

1986 ◽  
Vol 236 (3) ◽  
pp. 779-787 ◽  
Author(s):  
A P Halestrap ◽  
P T Quinlan ◽  
D E Whipps ◽  
A E Armston
Keyword(s):  
Liver Mitochondria ◽  
Ruthenium Red ◽  
Mitochondrial Swelling ◽  
Transport Systems ◽  
Matrix Volume ◽  
Specific Permeability ◽  
Mitochondrial Volume ◽  
Energy Dependent

The ability of alpha-adrenergic agonists and vasopressin to increase the mitochondrial volume in hepatocytes is dependent on the presence of extracellular Ca2+. Addition of Ca2+ to hormone-treated cells incubated in the absence of Ca2+ initiates mitochondrial swelling. In the presence of extracellular Ca2+, A23187 (7.5 microM) induces mitochondrial swelling and stimulates gluconeogenesis from L-lactate. Isolated liver mitochondria incubated in KCl medium in the presence of 2.5 mM-phosphate undergo energy-dependent swelling, which is associated with electrogenic K+ uptake and reaches an equilibrium when the volume has increased to about 1.3-1.5 microliter/mg of protein. This K+-dependent swelling is stimulated by the presence of 0.3-1.0 microM-Ca2+, leading to an increase in matrix volume at equilibrium that is dependent on [Ca2+]. Ca2+-activated K+-dependent swelling requires phosphate and shows a strong preference for K+ over Na+, Li+ or choline. It is not associated with either uncoupling of mitochondria or any non-specific permeability changes and cannot be produced by Ba2+, Mn2+ or Sr2+. Ca2+-activated K+-dependent swelling is not prevented by any known inhibitors of plasma-membrane ion-transport systems, nor by inhibitors of mitochondrial phospholipase A2. Swelling is inhibited by 65% and 35% by 1 mM-ATP and 100 microM-quinine respectively. The effect of Ca2+ is blocked by Ruthenium Red (5 micrograms/ml) at low [Ca2+]. Spermine (0.25 mM) enhanced the swelling seen on addition of Ca2+, correlating with its ability to increase Ca2+ uptake into the mitochondria as measured by using Arsenazo-III. Mitochondria derived from rats treated with glucagon showed less swelling than did control mitochondria. In the presence of Ruthenium Red and higher [Ca2+], the mitochondria from hormone-treated animals showed greater swelling than did control mitochondria. These data imply that an increase in intramitochondrial [Ca2+] can increase the electrogenic flux of K+ into mitochondria by an unknown mechanism and thereby cause swelling. It is proposed that this is the mechanism by which alpha-agonists and vasopressin cause an increase in mitochondrial volume in situ.

Effects of cold stress on mitochondrial oxidative phosphorylation

1960 ◽  
Vol 199 (1) ◽  
pp. 201-202 ◽  
Author(s):  
Judith Patkin ◽  
E. J. Masoro
Keyword(s):  
Oxidative Phosphorylation ◽  
Cold Stress ◽  
Liver Mitochondria ◽  
The Other ◽  
Mitochondrial Oxidative Phosphorylation ◽  
Tightly Coupled ◽  
Liver Homogenates ◽  
The One ◽  
Fasted Rats

The P:O ratio with succinate as substrate is the same for liver mitochondria from ‘cold-fasted’ rats as it is for mitochondria from control rats. Glucose-hexokinase acceptor studies with either succinate or glutamate as substrate indicate that the oxidative phosphorylating system is about as tightly coupled in the liver mitochondria from cold-fasted rats as it is in those from control rats. These results were surprising since earlier work with liver homogenates indicated that the efficiency of oxidative phosphorylation is markedly reduced in the homogenate from cold-fasted rats. The possible reasons for these differences in results with homogenates on the one hand and mitochondria on the other are discussed. The use of mitochondrial activities as an index of the efficiency of oxidative phosphorylation in vivo is also discussed.

Swelling of Fresh and Aged Liver Mitochondria as affected by Succinate, Adenine Nucleotides and Thyroxine

Nature ◽  
1960 ◽  
Vol 186 (4724) ◽  
pp. 556-558 ◽  
Author(s):  
P. EMMELOT ◽  
C. J. BOS ◽  
P. J. BROMBACHER ◽  
I. H. M. REYERS
Keyword(s):  
Adenine Nucleotides ◽  
Liver Mitochondria
Sign in / Sign up

Export Citation Format

Share Document