scholarly journals Xylitol metabolism in the isolated perfused rat liver

1973 ◽  
Vol 134 (2) ◽  
pp. 437-443 ◽  
Author(s):  
H. F. Woods ◽  
H. A. Krebs
Keyword(s):  
Main Product ◽  
Adenine Nucleotides ◽  
Lactate Production ◽  
Isolated Perfused Rat Liver ◽  
Perfused Rat Liver ◽  
Atp Content ◽  
Control Value ◽  
Lactate And Pyruvate ◽  
The Mean ◽  
Pyruvate Ratio

1. Loading the isolated perfused liver from well-fed rats with xylitol (20mm) caused a depletion of adenine nucleotides and Pi and an accumulation of α-glycerophosphate. The ATP content fell to 66% of the control value after 10min and to 32% after 80min. The ADP and AMP contents also fell. After 80min 63% of the total adenine nucleotides and 59% of the Pi had been lost. 2. The α-glycerophosphate content rose from 0.13 to 4.74μmol/g at 10min and reached 8.02μmol/g at 40min. 3. Xylitol was rapidly metabolized, the main products being glucose, lactate and pyruvate. 4. The [lactate]/[pyruvate] ratio in the presence of xylitol rose to 30–40. 5. On perfusion of livers from starved animals the main product of xylitol metabolism was glucose and the mean ratio xylitol removed/glucose formed was 1.29 (corrected for endogenous glucose and lactate production). This is close to the predicted value of 1.2. 6. Evidence is presented indicating that the loss of adenine nucleotides caused by xylitol is not due to the increased ATP consumption but to the accumulation of α-glycerophosphate and depletion of Pi. 7. The loss of adenine nucleotides accounts for the hyperuricaemia which can occur after xylitol infusion in man. 8. The relevance of the findings to the clinical use of xylitol as an energy source is discussed.

scholarly journals The effect of glycerol and dihydroxyacetone on hepatic adenine nucleotides

1973 ◽  
Vol 132 (1) ◽  
pp. 55-60 ◽  
Author(s):  
H. F. Woods ◽  
H. A. Krebs
Keyword(s):  
Adenine Nucleotide ◽  
Adenine Nucleotides ◽  
Isolated Perfused Rat Liver ◽  
Perfused Rat Liver ◽  
Phosphate Content ◽  
Perfusion Medium ◽  
Control Value ◽  
Lactate And Pyruvate ◽  
Metabolite Content ◽  
Pyruvate Ratio

1. The changes in the metabolite content in the isolated perfused rat liver and in the perfusion medium were measured after loading the liver with glycerol or dihydroxyacetone. 2. Glycerol was rapidly taken up by livers from fed and starved rats; glucose, lactate and pyruvate were discharged into the medium. The [lactate]/[pyruvate] ratio in the medium rose from 10 to 30 and in the tissue from 9.6 to 36.6. 3. The most striking effects of glycerol loading were: (i) the accumulation in the liver of α-glycerophosphate, which increased from 0.13 to 8.45μmol/g at 40min; (ii) the decrease in the concentration of adenine nucleotides to 70% of the control value at 40min. 4. The Pi content of the tissue also fell, from 4.25 to 2.31μmol/g at 10min, but the sum of the phosphates measured rose from the normal value of 13.8 to 18.8μmol/g at 40min, because of an uptake of Pi from the medium. 5. Omission of phosphate from the standard perfusion medium increased the depletion of adenine nucleotides on glycerol loading. 6. Dihydroxyacetone was more rapidly metabolized than glycerol. Again glucose, lactate and pyruvate were the main products. The [lactate]/[pyruvate] ratio remained below 10. 7. Dihydroxyacetone caused an increase of the fructose 1-phosphate content from 0.23 to 0.39μmol/g at 10min. The adenine nucleotide content of the tissue was not significantly decreased by dihydroxyacetone loading. 8. The rate of removal of both glycerol and dihydroxyacetone was about 60% greater in the livers from fed than in those from starved animals. 9. The results extend previous findings by Burch et al. (1970), who administered glycerol and dihydroxyacetone intraperitoneally.

scholarly journals The effects of halothane (2-bromo-2-chloro-1,1,1-trifluoroethane) on glycolysis and biosynthetic processes of the isolated perfused rat liver

1972 ◽  
Vol 128 (3) ◽  
pp. 711-720 ◽  
Author(s):  
J. F. Biebuyck ◽  
Patricia Lund ◽  
H. A. Krebs
Keyword(s):  
Rat Liver ◽  
Lactate Production ◽  
Fold Increase ◽  
Isolated Perfused Rat Liver ◽  
Urea Synthesis ◽  
Perfused Rat Liver ◽  
Anaesthetic Agents ◽  
Metabolic Functions ◽  
Tissue Content ◽  
Gluconeogenesis From Alanine

1. With reference to the post-operative dysfunction of the liver observed after halothane anaesthesia, the effects of the anaesthetic on some metabolic functions were studied in the isolated perfused rat liver. Oxygen uptake, glycolysis, gluconeogenesis and urea synthesis were affected by halothane at a concentration (2.5% of the gas phase) within the range used in clinical anaesthesia. 2. At this concentration of halothane uptake of oxygen was inhibited in livers from both fed and starved rats. 3. In livers from fed rats there was a 16-fold increase in lactate production. This was accompanied by a fivefold decrease in the tissue content of 2-oxoglutarate and a more than twofold decrease in citrate. The calculated [free NAD+]/[free NADH] ratio in both cytoplasm and mitochondria was lower in the halothane-exposed livers than in controls. 4. In livers of starved rats the rate of gluconeogenesis from lactate was decreased by halothane to 30% of the control rate. 5. Halothane inhibited gluconeogenesis from alanine and propionate to the same extent as from lactate, whereas glucose formation from dihydroxyacetone, glycerol, fructose and sorbitol was relatively unaffected. 6. During gluconeogenesis from 10mm-lactate the tissue content of ATP was decreased by 50%, glutamate by 50% and 2-oxoglutarate was decreased eightfold in the halothane-exposed livers. 7. Halothane decreased urea synthesis in the presence of 10mm-NH4Cl and 2mm-ornithine to 15% of the control rate. 8. The inhibitions of gluconeogenesis and urea synthesis were completely abolished within 15min of withdrawal of the anaesthetic. 9. The stimulation of uptake of oxygen brought about by the addition of lactate or precursors of urea was abolished by halothane. 10. Effects on gluconeogenesis similar to those of halothane occurred in livers exposed to the anaesthetic methoxyflurane, although normal rates were not restored on withdrawal of the drug. Other anaesthetic agents tested (ketamine–HCl and trichloroethylene) decreased gluconeogenesis to 66% of the control rate. 11. The inhibitory effects of halothane are consistent with an interference at the stage of the NADH dehydrogenase of the electron-transport chain.

scholarly journals Metabolic studies in experimental liver disease resulting from d(+)-galactosamine administration

1972 ◽  
Vol 130 (1) ◽  
pp. 37-44 ◽  
Author(s):  
Christopher O. Record ◽  
K. G. M. M. Alberti ◽  
Dermot H. Williamson
Keyword(s):  
Phosphoenolpyruvate Carboxylase ◽  
Ketone Bodies ◽  
Soluble Fraction ◽  
Mass Action ◽  
Significant Elevation ◽  
Control Value ◽  
Glucose Synthesis ◽  
Lactate And Pyruvate ◽  
Experimental Liver ◽  
Pyruvate Ratio

1. In confirmation of previous work, administration of d(+)-galactosamine (0.5–0.75g/kg body wt.) to rats caused a hepatitis with histological evidence of liver damage and a 9-fold rise in aspartate aminotransferase activity in serum. 2. There was a significant elevation of blood lactate and pyruvate concentrations in 24h-starved rats treated with galactosamine but no change in the [lactate]/[pyruvate] ratio. 3-Hydroxybutyrate and acetoacetate concentrations in blood were decreased. 3. The changes in the concentrations of lactate, pyruvate and ketone bodies in the freeze-clamped liver were parallel to those observed in the blood. 4. In the livers of 24h-starved galactosamine-treated rats there were large increases in the concentrations of alanine (3-fold), citrate (5-fold), 2-oxoglutarate (4-fold), with smaller increases in malate, glutamate and aspartate. There was a 4-fold rise in the value of the mass-action ratio of the alanine aminotransferase system in the livers of galactosamine-treated rats when compared to controls. 5. There was a significant decrease in the activities of aspartate and alanine aminotransferases in the cytoplasm and the soluble fraction of sonicated homogenates of the livers of rats treated with galactosamine. The activity of phosphoenolpyruvate carboxylase was decreased by 75% of the control value. 6. Glucose synthesis from lactate in perfused livers from galactosamine-treated rats was inhibited 39% when compared with controls. 7. The results indicate that the conversion of lactate into glucose is decreased in the livers of galactosamine-treated rats and that this decrease may be due to the loss of phosphoenolpyruvate carboxylase from damaged hepatocytes.

scholarly journals NH4+ metabolism and the intracellular pH in isolated perfused rat liver

1993 ◽  
Vol 293 (3) ◽  
pp. 667-673 ◽  
Author(s):  
J Zange ◽  
J Gronczewski ◽  
A W H Jans
Keyword(s):  
Intracellular Ph ◽  
Rat Liver ◽  
Isolated Hepatocytes ◽  
Isolated Perfused Rat Liver ◽  
Small Range ◽  
Perfused Rat Liver ◽  
Atp Content ◽  
Intracellular Acidification ◽  
Subsequent Conversion ◽  
Intracellular Alkalinization

The effects of NH4+ on the intracellular pH (pHi) and on the ATP content in isolated perfused rat liver were studied by 31P n.m.r. spectroscopy. In the initial phase of perfusion an average pHi of 7.29 +/- 0.04 was estimated. The presence of low (0.5 mmol/l) and high (10 mmol/l) doses of NH4Cl induced significant intracellular acidification by -0.06 +/- 0.03 and -0.11 +/- 0.03 pH unit respectively. This effect was in contrast with the transient intracellular alkalinization observed in preliminary studies on isolated hepatocytes, which was caused by a passive entry of NH3 by non-ionic diffusion and subsequent conversion into NH4+. During application of 0.5 mmol/l NH4Cl the liver released 0.54 +/- 0.06 mumol of urea/min per g into the perfusate. When the intracellular availability of HCO3- was decreased by acetazolamide (0.5 mmol/l) or by removal of HCO3- from the perfusion medium, the decrease in pHi by NH4Cl application was significantly lower than under control conditions. Furthermore, synthesis of urea was significantly inhibited by the decrease in intracellular HCO3-. Under these conditions, 10 mmol/l NH4Cl caused the transient alkalinization that was expected because of the passive uptake of uncharged NH3. Therefore, it is concluded that the intracellular acidification induced by NH4Cl is caused by the continuous utilization of intracellular HCO3- via the synthesis of urea. This metabolic effect on pHi dominates the effects of passive NH3 entry. The rate of urea formation depends on continuous efflux of H+, which is strictly limiting the degree of intracellular acidification within a small range. If the extrusion of H+ by the Na+/H+ exchanger was inhibited by amiloride (0.5 mmol/l) during the NH4Cl application, the decrease in pHi was amplified and the formation of urea was significantly inhibited. The application of NH4Cl at 0.5 or 10 mmol/l decreased the ATP content by 11% or 22% respectively.

Lactate and pyruvate gradients between red blood cells and plasma during acute asphyxia

1964 ◽  
Vol 19 (6) ◽  
pp. 1100-1104 ◽  
Author(s):  
Salha S. Daniel ◽  
Hisayo O. Morishima ◽  
L. Stanley James ◽  
Karlis Adamsons
Keyword(s):  
Sodium Lactate ◽  
Red Cells ◽  
Red Cell ◽  
Cell Ratio ◽  
Lactate And Pyruvate ◽  
The Mean ◽  
Endogenous Release ◽  
Pyruvate Ratio

The rate of equilibration of lactate and pyruvate between plasma and red cells has been studied during asphyxia and following addition of sodium lactate in vivo and in vitro. In the resting, well-oxygenated guinea pig, the mean plasma/red cell ratio of lactate was 1.55 and that of pyruvate 2.47. During asphyxia, the plasma/red cell ratio of lactate rose and that of pyruvate fell, indicating a delay in equilibration. Incomplete equilibration affected particularly the lactate/pyruvate ratio in the two compartments. Infused neutral sodium lactate penetrated the red cells at a rate comparable to that observed following endogenous release of lactic acid during acute asphyxia. In vitro at pH 6.8@#X2013;7.4 at 38 C, the time to 50% equilibration of lactate between plasma and cells of human blood was less than 2 min. It is concluded that during acute asphyxia and resuscitation whole blood values of lactate and pyruvate do not bear a constant relationship to those of plasma. lactate/pyruvate ratio Submitted on March 16, 1964

Effect of glycogenolytic agents on phosphorylase activity of perfused rat liver

1965 ◽  
Vol 208 (2) ◽  
pp. 317-323 ◽  
Author(s):  
Robert A. Levine
Keyword(s):  
Rat Liver ◽  
Cyclic Nucleotide ◽  
Adenine Nucleotides ◽  
Adenosine Monophosphate ◽  
Isolated Perfused Rat Liver ◽  
Perfused Rat Liver ◽  
Adrenocorticotrophic Hormone ◽  
Phosphorylase Activity ◽  
Glycogen Breakdown ◽  
Intact Rats

The effect of glycogenolytic agents on phosphorylase activity has been studied in the isolated perfused rat liver. Evidence is presented showing that endoportal administration of 10–6m glucagon, 10–5 m epinephrine, and 10–3 M cyclic 3',5'-adenosine monophosphate (3',5'-AMP) induced glycogenolysis, hyperglycemia, and increase in liver phosphorylase activity, usually within 1 hr after the onset of infusion. ATP, 10–3m, also caused glycogenolysis, but the onset was slower than with the cyclic nucleotide, and phosphorylase activation was inconstant Hyperglycemic effects of these two adenine nucleotides were also demonstrated in intact rats. Anoxia and hypoxia caused substantial glycogenolysis but did not stimulate phosphorylase activity, implying that some other mechanism accounts for the glycogen breakdown induced by reduced oxygen tension. Glycogenolysis and phosphorylase activation were not produced by administration of 10–2 M 5'-AMP, 10–4 M isoproterenol, adrenocorticotrophic hormone, or insulin.

Studies on bile secretion with the aid of the isolated perfused rat liver I. Inhibitory action of sporidesmin and icterogenin

1974 ◽  
Vol 186 (1085) ◽  
pp. 333-356 ◽  
Keyword(s):  
Rat Liver ◽  
Electron Micrographs ◽  
Bile Flow ◽  
Bile Secretion ◽  
Isolated Perfused Rat Liver ◽  
Perfused Rat Liver ◽  
Morphological Examination ◽  
Buffer Solution ◽  
Canalicular Membrane ◽  
Pyruvate Ratio

An isolated perfused rat liver preparation has been developed to aid the study of the mechanisms underlying the secretion of bile and the cholestatic actions of two naturally occurring agents, icterogenin and sporidesmin. The perfused liver produced bile for 3-5 h at a steady rate slightly above that observed in intact rats possessing external biliary cannulae. During this period of perfusion detailed biochemical and physiological studies on the behaviour of the liver were carried out. Morphological examination of the livers after several hours of perfusion was performed by means of electron microscopy and quantitative analysis of the pictures for certain structural elements has been performed. The addition of ethanol (final concentration 27 mM) to control perfusion had no significant effect on bile flow or liver morphology except that there was a decrease in the numbers of multi- and mono-vesicular bodies and in their relative proportions in the cytoplasm. There was a large though transient increase in perfusate lactate to pyruvate ratio and a sharp fall in the perfusate pH. Sporidesmin (2 mg in ethanol-buffer solution) rapidly decreased bile flow, and retarded the increase in the lactate to pyruvate ratio and the decrease in the pH of the perfusate seen in ethanol controls. Electron micrographs of the livers following sporidesmin administration showed large regions of the bile canaliculi devoid of microvilli and there was the appearance in the cytoplasm of lysosomal-like structures containing numerous glycogen granules. Icterogenin (4 mg in ethanol-buffer solution) produced a rapid cholestasis, inhibited the changes in the lactate to pyruvate ratio and the perfusate pH seen in the ethanol control preparations. Electron micrographs of the icterogenin-treated livers revealed changes in the canalicular membrane, extrusion of material into the canalicular lumen and aggregation of lysosomes in the cytoplasm. These studies suggest that bile flow in the rat is seriously affected by disturbances to the canalicular membrane, and preliminary biochemical investigations of these disturbances are reported here.

scholarly journals The cause of hepatic accumulation of fructose 1-phosphate on fructose loading

1970 ◽  
Vol 119 (3) ◽  
pp. 501-510 ◽  
Author(s):  
H. F. Woods ◽  
L. V. Eggleston ◽  
H. A. Krebs
Keyword(s):  
Adenine Nucleotides ◽  
Amp Deaminase ◽  
Atp Content ◽  
Perfusion Medium ◽  
Normal Value ◽  
Rate Of Penetration ◽  
Physiological Limits ◽  
Transient Decrease ◽  
Metabolite Content ◽  
Pyruvate Ratio

1. The changes in the metabolite content in freeze-clamped livers of fed rats occurring on perfusion with 10mm-d-fructose have been examined. 2. The most striking effects of fructose were an accumulation of fructose 1-phosphate, as already known, up to 8.7μmol/g of liver within 10min, a loss of total adenine nucleotides (up to 35% after 40min) with a decrease in the ATP content to 23% within 10min, a sevenfold rise in the concentration of IMP to 1.1μmol/g and an eightfold rise of α-glycerophosphate to 1.1μmol/g. 3. There was a transient decrease in Pi from 4.2 to 1.7μmol/g. Within 40min the Pi content recovered to the normal value, probably because of an uptake of Pi from the perfusion medium. 4. The degradation of the adenine nucleotides beyond the stage of AMP can be accounted for by the decrease of ATP and Pi. As ATP inhibits 5-nucleotidase, and as Pi inhibits AMP deaminase any AMP arising in the tissue is liable to undergo dephosphorylation or deamination under the conditions occurring after fructose loading. 5. The content of lactate increased to 4.3μmol/g at 80min; pyruvate also increased and the [lactate]/[pyruvate] ratio remained within physiological limits. 6. The concentration of free fructose within the liver remained much below that in the perfusion medium, indicating that the rate of penetration of fructose into the tissue was lower than the rate of utilization. 7. The fission of fructose 1-phosphate by liver aldolase is inhibited by several phosphorylated intermediates, especially by IMP. This inhibition is competitive with a Ki of 0.1mm. 8. The maximal rates of the enzymes synthesizing and splitting fructose 1-phosphate are about equal. The accumulation of fructose 1-phosphate on fructose loading is due to the inhibition of the fission of fructose 1-phosphate by the IMP arising from the degradation of the adenine nucleotides.

Lung as a model for evaluation of critical intracellular PO2 and PCO

1981 ◽  
Vol 241 (1) ◽  
pp. E47-E50 ◽  
Author(s):  
A. B. Fisher ◽  
C. Dodia
Keyword(s):  
Gas Exchange ◽  
Lactate Production ◽  
Mitochondrial Respiratory Chain ◽  
Rat Lung ◽  
Atp Content ◽  
High Affinity ◽  
Alveolar Hypoxia ◽  
Lactate And Pyruvate ◽  
The Relationship ◽  
Co Concentrations

The relationship between cellular metabolism and tissue O2 tension was investigated using the isolated perfused rat lung. Lungs were ventilated with gas mixtures of varying PO2 under conditions of no net gas exchange so that alveolar and lung parenchymal gas tensions were in approximate equilibrium. When alveolar PO2 was reduced to 0.7 mmHg, there were significant increases in lung lactate production and perfusate lactate/pyruvate, and decreases in lung tissue ATP content and ATP/ADP. Metabolic parameters were unchanged by alveolar hypoxia when alveolar PO2 was 7 mmHg or greater. Changes of complete anoxia required a PO2 less than 0.04 mmHg. To determine competition between O2 and CO in lung metabolism, alveolar O2 was maintained at 5% and CO was varied from 0 to 90%. Significant changes in production of lactate and pyruvate and tissue ATP content occurred with an alveolar CO of 75% (CO/O2 = 15) but not with CO concentrations of 50%, (CO/O2 = 10) or less. These results with an intact organ confirm previous data with subcellular systems showing a high affinity of the mitochondrial respiratory chain for O2, and indicate that the metabolic changes of hypoxia do not occur until intracellular PO2 approaches 1 mmHg or the CO/O2 exceeds 10.

A Comparison of Plasminogen Activators Derived from Rat Plasma, Primary Rat Hepatocytes and Isolated Perfused Rat Liver

1982 ◽  
Vol 47 (02) ◽  
pp. 166-172 ◽  
Author(s):  
Yoav Sharoni ◽  
Maria C Topal ◽  
Patricia R Tuttle ◽  
Henry Berger
Keyword(s):  
Rat Liver ◽  
Isoelectric Point ◽  
Rat Hepatocytes ◽  
Cell Types ◽  
Plasminogen Activators ◽  
Rat Plasma ◽  
Isolated Perfused Rat Liver ◽  
Perfused Rat Liver ◽  
Molecular Weights ◽  
Physiological Relevance

SummaryOf the two cell types it was possible to culture from the dissociated rat liver, hepatocytes and Kupffer cells, only the former were fibrinolytically active. Rat hepatocytes during the first 24 hr in culture secreted two plasminogen activators with molecular weights identical to those found in rat plasma, an 80,000-dalton form (PA-80) and a 45,000-dalton form (PA-45). Partially purified preparations of plasminogen activators from both sources were subjected to isoelectric focusing (IEF) to compare characteristics further. There were three distinct peaks of PA-45 in each preparation with isoelectric points of 7.1, 7.2 and 7.4; all electrophoretic forms had the same low affinity to fibrin. PA-80 from both sources displayed similar IEF profiles with forms ranging from pH values of 7 to 8, all with the same high affinity to fibrin. The major form of PA-80 in the plasma preparation had an isoelectric point of 7.9 whereas that in the hepatocyte preparation had an isoelectric point of 7.6. The isolated perfused rat liver was also shown to produce both PA-80 and PA-45 emphasizing the physiological relevance of the findings with hepatocytes. It is concluded that in the rat hepatocytes contribute to the plasma profile with regard to the plasminogen activator content.

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