Uptake of individual amino acids by perfused rat liver: effect of acute uremia

1970 ◽  
Vol 219 (3) ◽  
pp. 649-653 ◽  
Author(s):  
WW Lacy
Keyword(s):  
Amino Acids ◽  
Rat Liver ◽  
Perfused Rat Liver

scholarly journals Accumulation of amino acids by the perfused rat liver in the presence of ethanol

1973 ◽  
Vol 134 (3) ◽  
pp. 697-705 ◽  
Author(s):  
Hans A. Krebs ◽  
Reginald Hems ◽  
Patricia Lund
Keyword(s):  
Amino Acids ◽  
Rat Liver ◽  
Major Effect ◽  
Major Product ◽  
Control Mechanisms ◽  
Perfused Rat Liver ◽  
Carbamoyl Phosphate ◽  
Lactate Formation ◽  
Gluconeogenesis From Alanine ◽  
Almost All

1. The rate of gluconeogenesis from alanine in the perfused rat liver is affected by the presence of other metabolizable substances, especially fatty acids, ornithine and ethanol. Gluconeogenesis is accelerated by oleate and by ornithine. When both oleate and ornithine were present the acceleration was greater than expected on the basis of mere additive effects. 2. Much NH3 and some urea were formed from alanine when no ornithine was added. With ornithine almost all the nitrogen released from alanine appeared as urea. 3. Lactate was a major product of alanine metabolism. Addition of oleate, and especially of oleate plus ornithine, decreased lactate formation. 4. Ethanol had no major effect on gluconeogenesis from alanine when this was the sole added precursor. Gluconeogenesis was strongly inhibited (87%) when oleate was also added, but ethanol greatly accelerated gluconeogenesis when ornithine was added together with alanine. 5. In the absence of ethanol the alanine carbon and alanine nitrogen removed were essentially recovered in the form of glucose, lactate, pyruvate, NH3 and urea. 6. In the presence of ethanol the balance of both alanine carbon and alanine nitrogen showed substantial deficits. These deficits were largely accounted for by the formation of aspartate and glutamine, the formation of which was increased two- to three-fold. 7. When alanine was replaced by lactate plus NH4Cl, ethanol also caused a major accumulation of amino acids, especially of aspartate and alanine. 8. Earlier apparently discrepant results on the effects of ethanol on gluconeogenesis from alanine are explained by the fact that under well defined conditions ethanol can inhibit, or accelerate, or be without major effect on the rate of gluconeogenesis. 9. It is pointed out that in the synthesis of urea through the ornithine cycle half of the nitrogen must be supplied in the form of asparate and half in the form of carbamoyl phosphate. The accumulation of aspartate and other amino acids suggests that ethanol interferes with the control mechanisms which regulate the stoicheiometric formation of aspartate and carbamoyl phosphate.

Utilisation of Amino Acids by the Perfused Rat Liver

1976 ◽  
Vol 20 (6) ◽  
pp. 404-414 ◽  
Author(s):  
D.A. Hems ◽  
M.G. Davies ◽  
A.J. Thomas ◽  
P.D. Whitton
Keyword(s):  
Amino Acids ◽  
Rat Liver ◽  
Perfused Rat Liver

Cell Volume Regulatory Responses of Isolated Perfused Rat Liver. The Effect of Amino Acids

1990 ◽  
Vol 371 (1) ◽  
pp. 493-502 ◽  
Author(s):  
Matthias WETTSTEIN ◽  
Stephan VOM DAHL ◽  
Florian LANG ◽  
Wolfgang GEROK ◽  
Dieter HÄUSSINGER
Keyword(s):  
Amino Acids ◽  
Cell Volume ◽  
Rat Liver ◽  
Isolated Perfused Rat Liver ◽  
Perfused Rat Liver

Proteolysis in homogenates of perfused rat liver: Responses to insulin, glucagon and amino acids

1973 ◽  
Vol 54 (1) ◽  
pp. 89-95 ◽  
Author(s):  
G.E. Mortimore ◽  
A.N. Neely ◽  
J.R. Cox ◽  
R.A. Guinivan
Keyword(s):  
Amino Acids ◽  
Rat Liver ◽  
Perfused Rat Liver

scholarly journals The effects of amino acids on albumin synthesis by the isolated perfused rat liver

1972 ◽  
Vol 129 (4) ◽  
pp. 805-809 ◽  
Author(s):  
L. Kelman ◽  
S. J. Saunders ◽  
S. Wicht ◽  
L. Frith ◽  
A. Corrigall ◽  
...  
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Rat Liver ◽  
Normal Values ◽  
Isolated Perfused Rat Liver ◽  
Perfused Rat Liver ◽  
Albumin Synthesis ◽  
Isoleucine Leucine ◽  
Blood Concentrations ◽  
Normal Peripheral Blood

Albumin synthesis was measured in the isolated perfused rat liver by using the livers of both well-fed and starved rats. Starvation markedly decreased albumin synthesis. The livers from starved rats were unable to increase synthesis rates after the addition to the perfusates of single amino acids or the addition of both glucagon and tryptophan. Arginine, asparagine, isoleucine, leucine, lysine, methionine, phenylalanine, proline, threonine, tryptophan and valine, added together to ten times their normal peripheral blood concentrations, restored synthesis rates to normal. The plasma aminogram (i.e. the relative concentrations, of amino acids) was altered by depriving rats of protein for 48h. The use of blood from the deprived rats as perfusate, instead of normal blood, decreased albumin synthesis rates significantly by livers obtained from well-fed rats. The addition of single amino acids, including the non-metabolizable amino acid, α-aminoisobutyric acid, to the above mixture increased albumin synthesis rates to normal values. It is concluded that amino acids play an important role in the control of albumin synthesis and that more than one mechanism is probably involved.

scholarly journals Hepatic synthesis of carnitine from protein-bound trimethyl-lysine. Lysosomal digestion of methyl-lysine-labelled asialo-fetuin

1976 ◽  
Vol 160 (1) ◽  
pp. 85-95 ◽  
Author(s):  
J LaBadie ◽  
W A Dunn ◽  
N N Aronson
Keyword(s):  
Amino Acids ◽  
Rat Liver ◽  
Free Amino ◽  
Isolated Perfused Rat Liver ◽  
Methyl Groups ◽  
Second Derivative ◽  
Perfused Rat Liver ◽  
Lysine Residues ◽  
Derivatives Of ◽  
Hepatic Synthesis

The biosynthesis of carnitine in the rat was studied by following the metabolism of two radioactive derivatives of asialo-fetuin. The first contained 14C-labelled methyl groups covalently bound to the 6-N-amino fraction of its lysine residues as 6-N-monomethyl- and dimethyl-lysine. By treating this protein with iodomethane, a second derivative was produced in which the radioactivity was preferentially incorporated as 6-N-[Me-14C]-trimethyl-lysine. These desialylated glycoproteins, like other asialo-proteins, were immediately cleared from the blood by rat liver. Within hepatocyte lysosomes, the 14C-labelled proteins were rapidly hydrolysed, producing free amino acids containing the various 6-N-[Me-14C]methylated lysine residues. The radioactive amino acids crossed the lysosomal membrane and were further metabolized in the cytosol. Carnitine was the major radioactive metabolite detected in extracts of the rat carcass and liver after intravenous injection of 6-N-[Me-14C]trimethyl-lysine-labelled asialo-fetuin. Within 3h, at least 34.6% of the trimethyl-lysine in the administered protein was converted into carnitine. Similarly, an isolated perfused rat liver converted 30% of the added peptide-bound trimethyl-lysine into carnitine within 90 min. On the other hand, in numerous attempts we failed to detect radioactive carnitine in both rat liver and carcass between 20 min and 22 h after injection of 6-N-[Me-14C]-monomethyl- and -dimethyl-lysine-labelled asialo-fetuin. These data provide evidence for a pathway of carnitine biosynthesis that involves trimethyl-lysine as a peptide-bound precursor as proposed by R.A. Cox & C.L. Hoppel [(1973) Biochem. J. 136, 1083-1090] and V. Tanphaichitr & H.P. Broquist [(1973) J. Biol. Chem. 248, 2176-2181]. The findings also show that rat liver can synthesize carnitine without the aid of other tissues, but cannot convert free partially methylated lysines into trimethyl-lysine.

Catabolism of arginine and ornithine in the perfused rat liver: effect of dietary protein and of glucagon

2000 ◽  
Vol 278 (3) ◽  
pp. E516-E521 ◽  
Author(s):  
Dan O'Sullivan ◽  
John T. Brosnan ◽  
Margaret E. Brosnan
Keyword(s):  
Amino Acids ◽  
Rat Liver ◽  
Dietary Protein ◽  
Reaction Pathway ◽  
Perfused Rat Liver ◽  
Ornithine Aminotransferase ◽  
Dibutyryl Camp ◽  
Similar Extent ◽  
Twofold Increase ◽  
Arginine Catabolism

The rates of oxidation of arginine and ornithine that occurred through a reaction pathway involving the enzyme ornithine aminotransferase (EC 2.6.1.13 ) were determined using14C-labeled amino acids in the isolated nonrecirculating perfused rat liver. At physiological concentrations of these amino acids, their catabolism is subject to chronic regulation by the level of protein consumed in the diet. 14CO2production from [U-14C]ornithine (0.1 mM) and from [U-14C]arginine (0.2 mM) was increased about fourfold in livers from rats fed 60% casein diets for 3–4 days. The catabolism of arginine in the perfused rat liver, but not that of ornithine, is subject to acute regulation by glucagon (10− 7 M), which stimulated arginine catabolism by ∼40%. Dibutyryl cAMP (0.1 mM) activated arginine catabolism to a similar extent. In retrograde perfusions, glucagon caused a twofold increase in the rate of arginine catabolism, suggesting an effect of glucagon on arginase in the perivenous cells.

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