scholarly journals Effects of ischaemia on metabolite concentrations in rat liver

1970 ◽  
Vol 117 (1) ◽  
pp. 91-96 ◽  
Author(s):  
J. T. Brosnan ◽  
H. A. Krebs ◽  
D. H. Williamson
Keyword(s):  
Glutamate Dehydrogenase ◽  
Rat Liver ◽  
Adenylate Kinase ◽  
Alanine Aminotransferase ◽  
Adenine Nucleotides ◽  
Lactate Concentration ◽  
The Other ◽  
Metabolite Concentrations ◽  
Combined Action

1. Changes in the concentrations of ammonia, glutamine, glutamate, 2-oxoglutarate, 3-hydroxybutyrate, acetoacetate, alanine, aspartate, malate, lactate, pyruvate, NAD+, NADH and adenine nucleotides were measured in freeze-clamped rat liver during ischaemia. 2. Although the concentrations of most of the metabolites changed rapidly during ischaemia the ratios [glutamate]/[2-oxoglutarate][NH4+] and [3-hydroxybutyrate]/[acetoacetate] changed equally and the value of the expression [3-hydroxybutyrate][2-oxoglutarate][NH4+]/[acetoacetate][glutamate] remained approximately constant, indicating that the 3-hydroxybutyrate dehydrogenase and glutamate dehydrogenase systems were at near-equilibrium with the mitochondrial NAD+ couple. 3. The value of the expression [alanine][oxoglutarate]/[pyruvate][glutamate] was about 0.7 in vivo and remained fairly constant during the ischaemic period of 5min, although the concentrations of alanine and oxoglutarate changed substantially. No explanation can be offered why the value of the ratio differed from that of the equilibrium constant of the alanine aminotransferase reaction, which is 1.48. 4. Injection of l-cycloserine 60min before the rats were killed increased the concentration of alanine in the liver fourfold and decreased the concentration of the other metabolites measured, except that of pyruvate. During ischaemia the concentration of alanine did not change but that of aspartate almost doubled. 5. After treatment with l-cycloserine the value in vivo of the expression [alanine][oxoglutarate]/[pyruvate][glutamate] rose from 0.7 to 2.4. During ischaemia the value returned to 0.8. 6. The effects of l-cycloserine are consistent with the assumption that it specifically inhibits alanine aminotransferase. 7. Most of the alanine formed during ischaemia is probably derived from pyruvate and from ammonia released by the deamination of adenine nucleotides and glutamine. The alanine is presumably formed by the combined action of glutamate dehydrogenase and alanine aminotransferase. 8. The rate of anaerobic glycolysis, calculated from the increase in the lactate concentration, was 1.3μmol/min per g fresh wt. 9. Although the concentrations of the adenine nucleotides changed rapidly during ischaemia, the ratio [ATP][AMP]/[ADP]2 remained constant at 0.54, indicating that adenylate kinase established near-equilibrium under these conditions.

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.

Autophagy of mitochondria in rat liver assessed by immunogold procedures.

1988 ◽  
Vol 36 (11) ◽  
pp. 1433-1440 ◽  
Author(s):  
E Knecht ◽  
A Martinez-Ramón ◽  
S Grisolia
Keyword(s):  
Glutamate Dehydrogenase ◽  
Rat Liver ◽  
Polyclonal Antibodies ◽  
Carbamoyl Phosphate ◽  
Autophagic Vacuoles ◽  
The Difference ◽  
In Vivo Administration ◽  
Phosphate Synthase

Glutamate dehydrogenase and carbamoyl phosphate synthase-I were localized in rat liver by immunogold procedures, using monoclonal and polyclonal antibodies. As expected, there was extensive labeling in mitochondria. Label was also found in lysosomal autophagic vacuoles. When autophagy was stimulated by in vivo administration of the anti-microtubular agent vinblastine we found that: (a) carbamoyl phosphate synthase-I and glutamate dehydrogenase could be found in mitochondria within autophagic vacuoles; (b) the carbamoyl phosphate synthase-I and glutamate dehydrogenase content of the mitochondria sequestered into autophagic vacuoles is the same as that of the nearby "free" mitochondria; and (c) in the whole liver, autophagic vacuoles contain c. 1.5 times more glutamate dehydrogenase than carbamoyl phosphate synthase-I, in contrast to mitochondria which have c. three times more carbamoyl phosphate synthase-I than glutamate dehydrogenase. The latter finding could explain, at least partially, the difference in half-lives of these enzymes.

scholarly journals Sources of ammonia for mammalian urea synthesis

1978 ◽  
Vol 176 (3) ◽  
pp. 733-737 ◽  
Author(s):  
H A Krebs ◽  
R Hems ◽  
P Lund ◽  
D Halliday ◽  
W W Read
Keyword(s):  
Glutamate Dehydrogenase ◽  
Initial Rate ◽  
Adenine Nucleotides ◽  
Rat Hepatocytes ◽  
The Other ◽  
Amino Group ◽  
Urea Synthesis ◽  
Purine Nucleotide ◽  
Carbamoyl Phosphate ◽  
Purine Nucleotide Cycle

The initial rate of incorporation of [15N]alanine into the 6-amino group of the adenine nucleotides in rat hepatocytes was about one-eighteenth of the rate of incorporation into urea. Thus the purine nucleotide cycle cannot provide most of the ammonia needed in urea synthesis for the carbamoyl phosphate synthase reaction (EC 2.7.2.5). On the other hand, contrary to the view expressed by McGivan & Chappell [(1975) FEBS Lett. 52, 1–7], the experiments support the view that hepatic glutamate dehydrogenase can supply the required ammonia.

scholarly journals Control of the redox state of the nicotinamide–adenine dinucleotide couple in rat liver cytoplasm

1972 ◽  
Vol 126 (1) ◽  
pp. 59-65 ◽  
Author(s):  
Marion Stubbs ◽  
R. L. Veech ◽  
H. A. Krebs
Keyword(s):  
Rat Liver ◽  
Redox State ◽  
Adenine Nucleotide ◽  
Adenine Nucleotides ◽  
Phosphoglycerate Kinase ◽  
Phosphorylation State ◽  
Crotyl Alcohol ◽  
Order Of Magnitude ◽  
The Individual

1. A study has been made of the ability of rat liver in vivo to maintain equilibrium in the combined glyceraldehyde 3-phosphate dehydrogenase, 3-phosphoglycerate kinase and lactate dehydrogenase reactions, i.e. in the system: [Formula: see text] Attempts were made to upset equilibrium. The [lactate]/[pyruvate] ratio was rapidly changed by injection of ethanol or crotyl alcohol, and the value of [ATP]/[ADP][HPO42-] was rapidly changed by injection of ethionine or carbonyl cyanide p-trifluoromethoxy-phenylhydrazone. 2. The concentrations of the metabolites occurring in the above equation were measured in freeze-clamped liver. 3. Although the injected agents caused large changes in the concentrations of the individual components, near-equilibrium in the system was maintained, as indicated by the fact that the value of [ATP]/[ADP][HPO42-], referred to as the phosphorylation state of the adenine nucleotides, measured directly agreed with the value calculated for equilibrium conditions from the above equation. 4. The results are discussed and taken to confirm that the order of magnitude of the value of the redox state of the cytoplasmic NAD couple in rat liver is controlled by the phosphorylation state of the adenine nucleotide system.

scholarly journals Studies of the ethylation of rat liver transfer ribonucleic acid after administration of l-ethionine

1972 ◽  
Vol 128 (1) ◽  
pp. 59-68 ◽  
Author(s):  
A. E. Pegg
Keyword(s):  
Rat Liver ◽  
Ribonucleic Acid ◽  
Major Part ◽  
Actinomycin D ◽  
Major Product ◽  
The Other ◽  
Methyl Donor ◽  
Principal Product

1. The ethylated nucleosides present in tRNA isolated from the livers of rats treated with 0.5g of l-ethionine/kg body wt. were investigated. Evidence that this tRNA contained N2-ethylguanine, N2N2-diethylguanine, N2-ethyl-N2-methylguanine, 7-ethylguanine, two ethylated pyrimidines and ethylated ribose groups was obtained. 2. Ethylation of bacterial tRNA was catalysed by extracts containing tRNA methylases prepared from rat liver by using S-adenosyl-l-ethionine as an ethyl donor, but the rate of ethylation was 20 times less than the rate of methylation with S-adenosyl-l-methionine as a methyl donor. 3. The principal product of such ethylation in vitro was N2-ethylguanine and traces of the other ethylated guanines and pyrimidines found in tRNA isolated from rats treated with ethionine in vivo were also found. 1-Ethyladenine was not formed, although 1-methyl-adenine is a major product of methylation of bacterial tRNA by these extracts, and 1-ethyladenine was not present in the rat liver tRNA isolated from ethionine-treated animals. 4. After injection of actinomycin D (15mg/kg body wt.) or l-methionine (1.0g/kg body wt.) before the ethionine, ethylation of tRNA was diminished by about 80% but not completely abolished. Administration of 1-aminocyclopentanecarboxylic acid (2.5g/kg body wt.) to inhibit the formation of S-adenosyl-l-ethionine inhibited ethylation of tRNA by 44%. 5. These results suggest that not all of the ethylation of tRNA that occurs in the livers of rats treated with ethionine is mediated by the action of tRNA methylases acting with S-adenosyl-l-ethionine as a substrate, but that this pathway does occur and accounts for a major part of the observed ethylation. 6. The results are discussed with reference to ethionine-induced hepatocarcinogenesis.

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 Hepatic redox state and gluconeogenesis from lactate in vivo in the rat

1973 ◽  
Vol 132 (1) ◽  
pp. 19-25 ◽  
Author(s):  
Richard A. Hawkins ◽  
C. Roger S. Houghton ◽  
Dermot H. Williamson
Keyword(s):  
Redox State ◽  
Inferior Vena ◽  
Lactate Concentration ◽  
Vena Cava ◽  
Dihydroxyacetone Phosphate ◽  
Redox Couples ◽  
Metabolite Concentrations ◽  
Hepatic Redox State

1. To examine the role of the hepatic redox state on the rate of gluconeogenesis the effects of sodium crotonate injection (6mmol/kg body wt.) on rat liver metabolite concentrations and gluconeogenesis from lactate were studied in vivo. 2. Crotonate caused a marked oxidation of cytoplasmic and mitochondrial redox couples; decreases were observed in the ratios of [lactate]/[pyruvate], [glycerol 3-phosphate]/[dihydroxyacetone phosphate], [hydroxybutyrate]/[acetoacetate] and measured [NAD+]/[NADH]. 3. Increases occurred in the liver concentrations of all gluconeogenic intermediates from pyruvate through to glucose 6-phosphate, but there was no change in lactate concentration. 4. To determine whether gluconeogenesis from lactate was altered by the more-oxidized hepatic redox state l-[2-14C]lactic acid was infused into the inferior vena cava (50μmol/min per kg body wt.) and the incorporation of radioactivity into blood glucose was measured. 5. Administration of crotonate transiently decreased the rate of lactate incorporation into glucose but within a few minutes the rate of incorporation returned to that of the controls. 6. The results indicate that in these experiments alteration of the NAD+–NADH systems of cytoplasm and mitochondria to a more-oxidized state did not change the rate of gluconeogenesis.

Comparison of binding and removal of remnants of triglyceride-rich lipoproteins of intestinal and hepatic origin by rat liver in vitro

1982 ◽  
Vol 243 (5) ◽  
pp. G389-G395
Author(s):  
A. D. Cooper ◽  
M. A. Shrewsbury ◽  
S. K. Erickson
Keyword(s):  
Rat Liver ◽  
Plasma Membranes ◽  
Low Density Lipoproteins ◽  
The Other ◽  
Very Low Density Lipoproteins ◽  
Rat Liver Plasma Membranes ◽  
Chylomicron Remnants ◽  
Fold Excess

Chylomicrons were isolated from intestinal lymph and very low-density lipoproteins (VLDL) from the perfusate of isolated perfused livers. In vivo the initial phase of clearance of these particles was very rapid. Chylomicrons appeared to be cleared more quickly than VLDL (t1/2 = 3.7 +/- 1.4 vs. 10.6 +/- 4.0 min). Remnants were prepared from these particles in eviscerated rats and isolated using conditions under which contamination of particles from one organ by particles from the other organ was minimal. The removal of these remnant particles by isolated perfused livers was studied. VLDL remnants were removed more rapidly than the nascent VLDL. The removal of 125I-labeled VLDL remnants was inhibited by the presence of unlabeled VLDL remnants or chylomicron remnants in the perfusate. A 15- to 20-fold excess of either particle inhibited about 50% of the uptake of the labeled lipoprotein. The two types of remnants had comparable potency as competitors of uptake. Similarly, the two types of remnants inhibited uptake of a trace of labeled chylomicron remnants. The binding of these particles to rat liver plasma remnants. The binding of these particles to rat liver plasma membranes was also investigated. Both labeled chylomicron remnants and VLDL remnants bound specifically to the membranes, and either type of remnant displaced the binding of the other with equal potency. Taken together, these results indicate that chylomicron and VLDL remnants share the same hepatic removal mechanism and suggest that the rate of removal of a remnant is not a function of the organ of origin of the precursor lipoprotein.

Constitutive and Induced Synthesis of Heat Shock Proteins in Transplantable Hepatomas

1987 ◽  
Vol 73 (6) ◽  
pp. 559-565 ◽  
Author(s):  
Luisa Schiaffonati ◽  
Lidia Bardella ◽  
Gaetano Cairo ◽  
Emilia Rappocciolo ◽  
Lorenza Tacchini ◽  
...  
Keyword(s):  
Heat Shock ◽  
Heat Shock Proteins ◽  
Rat Liver ◽  
Growth Rates ◽  
The Other ◽  
Constitutive Synthesis ◽  
Shock Proteins ◽  
Slow Growing

The synthesis of heat shock proteins (HSP) was studied in rat liver and in a series of transplantable Morris hepatomas with different growth rates, subjected to heat shock in vivo and in vitro. Different from the liver, hepatomas synthesized HSP constitutively, i.e., also before exposure to heat. This constitutive synthesis was low and limited to one HSP in the slowest-growing tumor, more marked and involving other HSP in the intermediate- and fast-growing hepatomas. In tumor that synthesized HSP constitutively, the induction of HSP in response to heat was proportionately reduced. These patterns of reaction were essentially similar in vivo ad in vitro. The amount of HSP 68 was well correlated to the levels of its mRNA in liver and in all hepatomas, whereas the increase in HSP 89 was accompanied by a corresponding increase in the related mRNA in liver and in slow-growing hepatoma, not in the other tumors, thus suggesting a different mechanism of control of HSP 89 synthesis in the more malignant hepatomas.

Sign in / Sign up

Export Citation Format

Share Document