scholarly journals The effect of urea synthesis on extracellular pH in isolated perfused rat liver

1986 ◽  
Vol 236 (1) ◽  
pp. 261-265 ◽  
Author(s):  
D Häussinger ◽  
W Gerok ◽  
H Sies
Keyword(s):  
Liver Perfusion ◽  
Hepatic Metabolism ◽  
The Other ◽  
Isolated Perfused Rat Liver ◽  
Urea Synthesis ◽  
Perfused Rat Liver ◽  
Extracellular Acidification ◽  
Isolated Liver ◽  
Stimulation Of

In a non-recirculating system of isolated liver perfusion, stimulation of urea synthesis by NH4Cl is followed by a decrease of effluent pH by up to 0.2 pH unit. This effect is not observed when urea synthesis is inhibited by amino-oxyacetate or norvaline. When the urea formed by the liver is immediately hydrolysed with urease before the effluent perfusate reaches the pH electrode, the urea-synthesis-induced acidification is no longer observed. This indicates that accompanying alterations in hepatic metabolism after stimulation of urea synthesis, such as increased energy provision and consumption, are not responsible for the extracellular acidification, but that the effect is due to the formation of urea itself. The acidification of the extracellular space after stimulation of urea synthesis by NH4Cl is quantitatively explained by the consumption of 2 mol of HCO3-/mol of urea formed: 1 mol being incorporated into urea, the other being protonated to yield CO2 and H2O. The data match the theoretically predicted HCO3- consumption during ureogenesis and underline the role of hepatic urea synthesis for disposal of HCO3- by converting it into the excretable products CO2 and urea.

scholarly journals Ganglioside incorporation and release by the isolated perfused rat liver

1991 ◽  
Vol 274 (2) ◽  
pp. 581-585 ◽  
Author(s):  
S C Kivatinitz ◽  
A Miglio ◽  
R Ghidoni
Keyword(s):  
Rat Liver ◽  
The Other ◽  
Regulatory Role ◽  
Isolated Perfused Rat Liver ◽  
Order Kinetic ◽  
Perfused Rat Liver ◽  
Ganglioside Gm1 ◽  
First Order ◽  
Pseudo First Order

The fate of exogenous ganglioside GM1 labelled in the sphingosine moiety, [Sph-3H]GM1, administered as a pulse, in the isolated perfused rat liver was investigated. When a non-recirculating protocol was employed, the amount of radioactivity in the liver and perfusates was found to be dependent on the presence of BSA in the perfusion liquid and on the time elapsed after the administration of the ganglioside. When BSA was added to the perfusion liquid, less radioactivity was found in the liver and more in the perfusate at each time tested, for up to 1 h. The recovery of radioactivity in the perfusates followed a complex course which can be described by three pseudo-first-order kinetic constants. The constants, in order of decreasing velocity, are interpreted as: (a) the dilution of the labelled GM1 by the constant influx of perfusion liquid; (b) the washing off of GM1 loosely bound to the surface of liver cells; (c) the release of gangliosides from the liver. Process (b) was found to be faster in the presence of BSA, probably owing to the ability of BSA to bind gangliosides. The [Sph-3H]GM1 in the liver underwent metabolism, leading to the appearance of products of anabolic (GD1a, GD1b) and catabolic (GM2, GM3) origin; GD1a appeared before GM2 and GM3 but, at times longer than 10 min, GM2 and GM3 showed more radioactivity than GD1a. At a given time the distribution of the radioactivity in the perfusates was quite different from that of the liver. In fact, after 60 min GD1a was the only metabolite present in any amount, the other being GM3, the quantity of which was small. This indicates that the liver is able to release newly synthesized gangliosides quite specifically. When a recirculating protocol was used, there were more catabolites and less GD1a than with the non-recirculating protocol. A possible regulatory role of ganglioside re-internalization on their own metabolism in the liver is postulated.

scholarly journals Metabolism of ornithine, α-ketoglutarate and arginine in isolated perfused rat liver

1995 ◽  
Vol 73 (2) ◽  
pp. 227-239 ◽  
Author(s):  
Jean Pascal De Bandt ◽  
Luc Cynober ◽  
Soo Kyung Lim ◽  
Colette Coudray-Lucas ◽  
Raoul Poupon ◽  
...  
Keyword(s):  
Rat Liver ◽  
Hepatic Metabolism ◽  
Isolated Perfused Rat Liver ◽  
Trauma Patients ◽  
Perfused Rat Liver ◽  
Metabolic Interaction ◽  
Urea Production ◽  
Stimulation Of

Ornithine (Orn; α-ketoglutarate (αKG) salt) and arginine (Arg) supplementation of enteral diets has been advocated in the treatment of hypercatabolism of trauma patients, but both compounds are subject to extensive hepatic metabolism. To compare the metabolism of these two compounds and to evaluate the possible influence of the αKG moiety, livers were perfused with αKG, Orn, ornithine α-ketoglutarate (OKG) or Arg (n 6 in each group) for 1 h. Arg uptake was nearly fourfold higher than Orn uptake (690 (SD 162) ν. 178 (SD 30) nmol/min per g liver), and Orn uptake was not modified by αKG. Orn was totally metabolized by the liver, whereas Arg led to Orn release (408 (SD 159) nmol/min per g liver) and a threefold stimulation of urea production (Arg 1·44 (SD 0·22) ν. Orn 0·45 (SD 0.09) μol/min per g liver). αKG alone only increased hepatic aspartate uptake but, when associated with Orn as OKG, it led to an increase in giutamate release and in proiine content in the liver and to a decrease in proiine uptake. From these findings we conclude that (1) Arg load is extensively metabolized by the liver, inducing urea production, (2) in enteral use, Orn supplementation appears preferable to Arg as it is less ureogenic (as also recently demonstrated in vivo in stressed rats receiving isomolar amounts of Arg and Orn), (3) the liver participates in the Orn-αKG metabolic interaction, mostly in proiine metabolism, which occurs in the splanchnic area.

scholarly journals The role of insulin in the modulation of glucagon-dependent control of phenylalanine hydroxylation in isolated liver cells

1987 ◽  
Vol 242 (3) ◽  
pp. 655-660 ◽  
Author(s):  
M J Fisher ◽  
A J Dickson ◽  
C I Pogson
Keyword(s):  
Cyclic Amp ◽  
Insulin Action ◽  
Phenylalanine Hydroxylase ◽  
Liver Cells ◽  
Phosphorylation State ◽  
Isolated Liver Cells ◽  
The Impact ◽  
Isolated Liver ◽  
Stimulation Of

The stimulation of phenylalanine hydroxylation in isolated liver cells by sub-maximally effective concentrations of glucagon (less than 0.1 microM) is antagonized by insulin (0.1 nM-0.1 microM). This phenomenon is a consequence of a decrease in the glucagon-stimulated phosphorylation of phenylalanine hydroxylase from liver cells incubated in the presence of insulin. The impact of insulin on the phosphorylation state and activity of the hydroxylase is mimicked by incubation of liver cells in the presence of orthovanadate (10 microM). A series of cyclic AMP and cyclic GMP analogues enhanced phenylalanine hydroxylation: in each case insulin diminished the stimulation of flux. These results are discussed in the light of the characteristics of insulin action on other metabolic processes.

Analysis of Regulatory Factors for Urea Synthesis by Isolated Perfused Rat Liver

1975 ◽  
Vol 77 (3) ◽  
pp. 671-678 ◽  
Author(s):  
Takeyori SAHEKI ◽  
Michio TSUDA ◽  
Tomi TANAKA ◽  
Nobuhiko KATUNUMA
Keyword(s):  
Rat Liver ◽  
Isolated Perfused Rat Liver ◽  
Urea Synthesis ◽  
Perfused Rat Liver ◽  
Regulatory Factors

Role of neutrophils in ischemia/reperfusion liver injury. A study in the isolated perfused rat liver

1991 ◽  
Vol 13 ◽  
pp. S109
Author(s):  
O. Chazouillères ◽  
C. Legendre ◽  
M. Vaubourdolle ◽  
M.T. Bonnefis ◽  
C. Rey ◽  
...  
Keyword(s):  
Liver Injury ◽  
Rat Liver ◽  
Ischemia Reperfusion ◽  
Isolated Perfused Rat Liver ◽  
Perfused Rat Liver

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.

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