scholarly journals The effect of experimental diabetes on phenylalanine metabolism in isolated liver cells

1985 ◽  
Vol 227 (1) ◽  
pp. 169-175 ◽  
Author(s):  
M A Santana ◽  
M J Fisher ◽  
A J Bate ◽  
C I Pogson
Keyword(s):  
Enzyme Activity ◽  
Hormonal Regulation ◽  
Metabolic Flux ◽  
Phenylalanine Hydroxylase ◽  
Experimental Diabetes ◽  
Liver Cells ◽  
Enzyme Protein ◽  
Isolated Liver Cells ◽  
Phenylalanine Metabolism ◽  
Isolated Liver

Chronic (10-day) diabetes was associated with increased metabolic flux through phenylalanine hydroxylase in isolated liver cells. This flux was stimulated by 0.1 microM-glucagon, but not by 10 microM-noradrenaline; 0.1 microM-insulin affected neither basal nor glucagon-stimulated flux. The increased rate of phenylalanine hydroxylation in diabetes was accompanied by parallel increases in enzyme activity (as measured with artificial cofactor) and immunoreactive-enzyme-protein content. In contrast with total protein synthesis, which decreased, phenylalanine hydroxylase synthesis persisted at the control rate in cells from diabetic animals. These findings are discussed in relation to the hormonal regulation of the hydroxylase and the known metabolic consequences of chronic diabetes.

scholarly journals Phenylalanine metabolism in isolated rat liver cells. Effects of glucagon and diabetes

1981 ◽  
Vol 198 (3) ◽  
pp. 655-660 ◽  
Author(s):  
F P A Carr ◽  
C I Pogson
Keyword(s):  
Metabolic Flux ◽  
Phenylalanine Hydroxylase ◽  
Experimental Diabetes ◽  
Hydroxylase Activity ◽  
Rat Liver Cells ◽  
Phenylalanine Metabolism ◽  
The Relationship ◽  
Substrate Concentrations ◽  
Isolated Liver

1. Methods are described for monitoring the metabolic flux through phenylalanine hydroxylase, the tyrosine catabolic pathway and phenylalanine: pyruvate transaminase in isolated liver cell incubations. 2. The relationship between hydroxylase flux and phenylalanine concentration is sigmoidal. 3. Glucagon increases hydroxylase activity at low, near-physiological, substrate concentrations only. The hormone does not affect the rate of formation of phenylpyruvate. 4. Experimental diabetes (for 10 days) increases phenylalanine catabolism, and this is further increased by glucagon. 5. These results are discussed in the light of the known mechanisms for control of phenylalanine hydroxylase activity in vitro.

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.

scholarly journals The polyamine-dependent modulation of phenylalanine hydroxylase phosphorylation state and enzymic activity in isolated liver cells

1986 ◽  
Vol 237 (1) ◽  
pp. 277-279 ◽  
Author(s):  
M J Fisher ◽  
A J Dickson ◽  
C I Pogson
Keyword(s):  
Protein Phosphatase ◽  
Phenylalanine Hydroxylase ◽  
Liver Cells ◽  
Enzymic Activity ◽  
Phosphorylation State ◽  
Isolated Liver Cells ◽  
Phosphatase 2A ◽  
Pre Treatment ◽  
Isolated Liver

The role of polyamines in the control of phenylalanine hydroxylase phosphorylation state and enzymic activity was investigated. Pre-treatment of liver cells with spermine (1 mM) abolishes the glucagon (1 nM)-stimulated increase in hydroxylase phosphorylation. Concurrently there is a decrease in phenylalanine hydroxylation flux, reflecting decreased enzyme activity; 50% inhibition occurs at approx. 10 microM-spermine. These results are discussed in the context of reports concerning the properties of protein phosphatase 2A.

scholarly journals Arachidonic acid synthesis studied in isolated liver cells

FEBS Letters ◽  
1981 ◽  
Vol 133 (2) ◽  
pp. 201-204 ◽  
Author(s):  
B.O. Christophersen ◽  
Jon Norseth
Keyword(s):  
Arachidonic Acid ◽  
Acid Synthesis ◽  
Liver Cells ◽  
Isolated Liver Cells ◽  
Isolated Liver

Decreased glucagon-stimulated cyclic AMP production by isolated liver cells of rats with type 2 diabetes

1983 ◽  
Vol 32 (1) ◽  
pp. 13-26 ◽  
Author(s):  
Bernard Portha ◽  
Hilda Chamras ◽  
Yvonne Broer ◽  
Luc Picon ◽  
Gabriel Rosselin
Keyword(s):  
Type 2 Diabetes ◽  
Cyclic Amp ◽  
Liver Cells ◽  
Isolated Liver Cells ◽  
Isolated Liver

scholarly journals Amylase in Isolated Liver Cells

1960 ◽  
Vol 235 (5) ◽  
pp. 1354-1358
Author(s):  
Robert L. McGeachin ◽  
Betty Ann Potter
Keyword(s):  
Liver Cells ◽  
Isolated Liver Cells ◽  
Isolated Liver
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