Regulation of pyruvate kinase by 6-phosphogluconate in isolated hepatocytes

1981 ◽  
Vol 240 (3) ◽  
pp. E279-E285
Author(s):  
S. B. Smith ◽  
R. A. Freedland
Keyword(s):  
Pyruvate Kinase ◽  
Parenchymal Cell ◽  
Isolated Hepatocytes ◽  
Hill Coefficient ◽  
Liver Parenchymal Cell ◽  
Liver Parenchymal ◽  
Highly Correlated ◽  
Parenchymal Cells ◽  
The Hill ◽  
Isolated Liver

Isolated liver parenchymal cells from rats fed a 65% sucrose diet for 14 days were incubated in the presence and absence of 10(-6) M glucagon. The pyruvate kinase obtained from homogenates of the glucagon-treated cells displayed and increased Ks 0.5 for phosphoenolpyruvate (P-enolpyruvate), as well as an increased Ka 0.5 for 6-phosphogluconate (6-P-gluconate), compared to pyruvate kinase from untreated cells. Additionally, glucagon treatment decreased the maximal stimulation of pyruvate kinase by 6-P-gluconate by approximately two-thirds and decreased the Hill coefficient value of pyruvate kinase for 6-P-gluconate from 1.76 to 1.56. 6-Aminonicotinamide, an inhibitor of 6-P-gluconate dehydrogenase, increased 6-P-gluconate levels in isolated liver parenchymal cells three- to sevenfold, depending on the substrates present. The flux of P-enolpyruvate through pyruvate kinase was increased from 18 to 40% in these preparations and was highly correlated with the increase in 6-P-gluconate levels. The results suggest that 6-P-gluconate could regulate pyruvate kinase activity in the intact liver parenchymal cell. Furthermore, the activator would be of greatest importance in the lipogenic animal.

l-Thyroxine enters the rat liver cell by simple diffusion

1983 ◽  
Vol 97 (2) ◽  
pp. 277-282 ◽  
Author(s):  
G. S. Rao ◽  
M. L. Rao
Keyword(s):  
Rat Liver ◽  
Arrhenius Plot ◽  
Parenchymal Cell ◽  
Liver Cells ◽  
Liver Parenchymal Cell ◽  
Simple Diffusion ◽  
Liver Parenchymal ◽  
Isolated Rat Liver ◽  
Centrifugation Technique ◽  
Parenchymal Cells

The mode of uptake of l-[125I]thyroxine by freshly isolated rat liver parenchymal cells was studied by a rapid centrifugation technique. Using conditions for measuring initial rates of uptake, uptake by liver cells was not saturable when exposed to hormone concentrations in the incubation medium ranging from 2 pmol/l to 10 μmol/l. The Arrhenius plot was linear from 2 to 37°C; the temperature coefficient was 1·4. The uptake of l-[125I]thyroxine by liver cells was 35% when compared with that of l-[125I]tri-iodothyronine. In the presence of 2·8% bovine serum albumin the rate of uptake of l-[125I]thyroxine by liver cells was reduced by 90%. These results suggest that l-[125I]thyroxine enters the rat liver parenchymal cell by simple diffusion and only the free hormone crosses the plasma membrane.

scholarly journals The effect of dietary protein deprivation on protein synthesis in the isolated liver parenchymal cell

1977 ◽  
Vol 38 (2) ◽  
pp. 255-260 ◽  
Author(s):  
Anne G. Grant ◽  
R. Hoffenberg
Keyword(s):  
Dietary Protein ◽  
Cell Function ◽  
Parenchymal Cell ◽  
Long Term Effects ◽  
Protein Deprivation ◽  
Liver Parenchymal Cell ◽  
Viable Cells ◽  
Parenchymal Cells ◽  
Isolated Liver

1. Parenchymal cells were isolated from the liver of rats that had been deprived of dietary protein for 3 weeks.2. The cells were two-thirds the diameter of those derived from livers of normal animals and consumed oxygen at a rate of 16.2±2.7 μl/h per 106 viable cells, half the normal value.3. Albumin and transferrin were synthesized at rates of 0.94±0.12 and 0.60±0.07 μg/h per 106 viable cells respectively and urea at a rate of 0.77±0.12 μg/h per 106 cells. This represents a 25-50% decrease in the rates of synthesis measured in cells isolated from normal livers.4. The results are discussed in relation to the long-term effects of malnutrition on liver cell function.

scholarly journals LIVER PARENCHYMAL CELL INJURY

1965 ◽  
Vol 25 (3) ◽  
pp. 53-75 ◽  
Author(s):  
Edward S. Reynolds
Keyword(s):  
Rat Liver ◽  
Inorganic Phosphate ◽  
Cell Injury ◽  
Parenchymal Cell ◽  
Mitochondrial Atpase ◽  
Liver Parenchymal Cell ◽  
Liver Parenchymal ◽  
Serum Inorganic Phosphate ◽  
Chemical Events ◽  
Parenchymal Cells

Accumulation of calcium in the mitochondria of rat liver parenchymal cells at 16 and 24 hours after poisoning with carbon tetrachloride is associated with an increase in amount of liver inorganic phosphate, the persistence of mitochondrial adenosine triphosphatase activity, and the formation of electron-opaque intramitochondrial masses in cells with increased calcium contents. These masses, which form within the mitochondrial matrix adjacent to internal mitochondrial membranes, resemble those observed in isolated mitochondria which accumulate calcium and inorganic phosphate; are present in a locus similar to that of electron opacities which result from electron-histochemical determination of mitochondrial ATPase activity; and differ in both appearance and position from matrix granules of normal mitochondria. After poisoning, normal matrix granules disappear from mitochondria prior to their accumulation of calcium. As calcium-associated electron-opaque intramitochondrial masses increase in size, mitochondria degenerate in appearance. At the same time, cytoplasmic membrane systems of mid-zonal and centrilobular cells are disrupted by degranulation of the rough endoplasmic reticulum and the formation of labyrinthine tubular aggregates. The increase in amount of inorganic phosphate in rat liver following poisoning is balanced by a decreased amount of phosphoprotein. These chemical events do not appear to be related, however, as the inorganic phosphate accumulated is derived from serum inorganic phosphate.

scholarly journals No major thermogenic role for (Na+ + K+)-dependent adenosine triphosphatase apparent in hepatocytes from hyperthyroid rats

1982 ◽  
Vol 202 (3) ◽  
pp. 661-665 ◽  
Author(s):  
D G Clark ◽  
M Brinkman ◽  
O H Filsell ◽  
S J Lewis ◽  
M N Berry
Keyword(s):  
Oxygen Consumption ◽  
Oxygen Uptake ◽  
Atpase Activity ◽  
Heat Production ◽  
Adenosine Triphosphatase ◽  
Heat Output ◽  
Liver Parenchymal ◽  
Dependent Atpase ◽  
Parenchymal Cells ◽  
Isolated Liver

(Na+ + K+)-dependent ATPase activity, heat production and oxygen consumption were increased by 59%, 62% and 75% respectively in hepatocytes from tri-iodothyronine-treated rats. Ouabain at concentrations of 1 and 10 mM decreased oxygen uptake by 2-8% in hepatocytes from euthyroid rats and by 5-15% in hepatocytes from hyperthyroid animals. Heat output was decreased by 4-9% with the glycoside in isolated liver parenchymal cells from the control animals and by 11% in the cells from the tri-iodothyronine-treated animals. These results do not support the hypothesis that hepatic (Na+ + K+)-ATPase plays a major role in increased heat production in hepatocytes from hyperthyroid rats.

scholarly journals Kinetic studies on the regulation of rabbit liver pyruvate kinase

1973 ◽  
Vol 131 (2) ◽  
pp. 287-301 ◽  
Author(s):  
M. G. Irving ◽  
J. F. Williams
Keyword(s):  
Pyruvate Kinase ◽  
Specific Activity ◽  
Deae Cellulose ◽  
Kinetic Studies ◽  
Rabbit Liver ◽  
Hill Coefficient ◽  
Saturation Curve ◽  
Low Concentrations ◽  
Ammonium Sulphate Fractionation ◽  
The Hill

Two kinetically distinct forms of pyruvate kinase (EC 2.7.1.40) were isolated from rabbit liver by using differential ammonium sulphate fractionation. The L or liver form, which is allosterically activated by fructose 1,6-diphosphate, was partially purified by DEAE-cellulose chromatography to give a maximum specific activity of 20 units/mg. The L form was allosterically activated by K+ and optimum activity was recorded with 30mm-K+, 4mm-MgADP-, with a MgADP-/ADP2- ratio of 50:1, but inhibition occurred with K+ concentrations in excess of 60mm. No inhibition occurred with either ATP or GTP when excess of Mg2+ was added to counteract chelation by these ligands. Alanine (2.5mm) caused 50% inhibition at low concentrations of phosphoenolpyruvate (0.15mm). The homotropic effector, phosphoenolpyruvate, exhibited a complex allosteric pattern (nH+2.5), and negative co-operative interactions were observed in the presence of low concentrations of this substrate. The degree of this co-operative interaction was pH-dependent, with the Hill coefficient increasing from 1.1 to 3.2 as the pH was raised from 6.5 to 8.0. Fructose 1,6-diphosphate interfered with the activation by univalent ions, markedly decreased the apparent Km for phosphoenolpyruvate from 1.2mm to 0.2mm, and transformed the phosphoenolpyruvate saturation curve into a hyperbola. Concentrations of fructose 1,6-diphosphate in excess of 0.5mm inhibited this stimulated reaction. The M or muscle-type form of the enzyme was not activated by fructose 1,6-diphosphate and gave a maximum specific activity of 0.3 unit/mg. A Michaelis–Menten response was obtained when phosphoenolpyruvate was the variable substrate (Km+0.125mm), and this form was inhibited by ATP, as well as alanine, even in the presence of excess of Mg2+.

scholarly journals Active Synthesis of Collagen by Albumin-Producing Liver Parenchymal Cell Clones in Culture

1978 ◽  
Vol 54 (7) ◽  
pp. 391-396 ◽  
Author(s):  
Ryu-ichiro HATA ◽  
Yoshifumi NINOMIYA ◽  
Yutaka NAGAI ◽  
Kooko SAKAKIBARA ◽  
Yutaka TSUKADA
Keyword(s):  
Parenchymal Cell ◽  
Active Synthesis ◽  
Liver Parenchymal Cell ◽  
Liver Parenchymal ◽  
Cell Clones
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