scholarly journals Compartmentation between glycolysis and gluconeogenesis in rat liver

1968 ◽  
Vol 110 (2) ◽  
pp. 303-312 ◽  
Author(s):  
C. J. Threlfall ◽  
D. F. Heath
Keyword(s):  
Kinetic Analysis ◽  
Intravenous Injection ◽  
Rat Liver ◽  
Isotopic Exchange ◽  
Direct Evidence ◽  
Specific Radioactivity ◽  
Glycolytic Pathway ◽  
Glucose Phosphorylation

1. The specific radioactivity–time relationships of glucose, glucose 6-phosphate, glycerol 1-phosphate and UDP-glucose were determined in rat liver after the intravenous injection of [U−14C]fructose, and a kinetic analysis was carried out. The glucose 6-phosphate pool was found to be compartmented into gluconeogenic and glycolytic components, and evidence was obtained that the triose phosphates were similarly compartmented. The glycolytic pathway was fed by glycogenolysis and glucose phosphorylation. There was no direct evidence that glycogenolysis fed only the glycolytic pathway, but this interpretation would make the liver resemble other organs in this respect. 2. UDP-glucose was not formed solely from gluconeogenic glucose 6-phosphate, as there was some dilution of label in the intervening glucose 1-phosphate pool, probably from glycogenolysis, though other pathways cannot be excluded. 3. The data cannot be explained by isotopic exchange.

Thyroxine transport from blood to brain via transthyretin synthesis in choroid plexus

1990 ◽  
Vol 258 (2) ◽  
pp. R338-R345 ◽  
Author(s):  
G. Schreiber ◽  
A. R. Aldred ◽  
A. Jaworowski ◽  
C. Nilsson ◽  
M. G. Achen ◽  
...  
Keyword(s):  
Cerebrospinal Fluid ◽  
Thyroid Hormones ◽  
Choroid Plexus ◽  
Intravenous Injection ◽  
Rat Liver ◽  
Specific Radioactivity ◽  
Perfusion Medium ◽  
The Brain

The transport of thyroxine from the bloodstream to the brain and the synthesis and secretion of transthyretin (formerly called prealbumin) were studied in rats and in sheep choroid plexus perfused in vitro. Rat choroid plexus contained 4.4 micrograms and rat liver 0.39 micrograms transthyretin mRNA per gram wet tissue. The specific radioactivity of transthyretin isolated from cerebrospinal fluid of rats 60 min after intravenous injection of [14C]leucine was greater than 50 times that of transthyretin from serum. After adding [14C]leucine to the perfusion medium of an in vitro perfused sheep choroid plexus, highly radioactive transthyretin was isolated from freshly secreted cerebrospinal fluid collected from the exposed choroid plexus surface. Secretion of newly synthesized transthyretin into the perfusion medium could not be demonstrated. After intravenous injection of [125I]-thyroxine into rats, a maximum in the curve of radioactivity in tissue plotted against time after injection was observed first for choroid plexus, thereafter for cerebrospinal fluid, and still later for cortex and striatum. Based on the obtained data, a hypothesis is derived for the mechanism of the transport of thyroid hormones from the bloodstream to the brain involving transthyretin synthesized in choroid plexus and secreted into the cerebrospinal fluid.

The Distribution of [14C]Cholesterol in Muscle and Skin of Rhesus Monkeys after Intravenous Injection

1976 ◽  
Vol 50 (4) ◽  
pp. 307-310
Author(s):  
C. D. Moutafis ◽  
N. B. Myant
Keyword(s):  
Intravenous Injection ◽  
Rhesus Monkeys ◽  
Plasma Cholesterol ◽  
Specific Radioactivity ◽  
Compartment System ◽  
Local Synthesis ◽  
Single Intravenous Injection ◽  
Small Pool ◽  
Slow Turnover

1. The specific radioactivity of [14C]cholesterol in plasma and in serial biopsies of muscle and skin was measured in Rhesus monkeys for 156 days after a single intravenous injection of [14C]cholesterol. 2. Analysis of the specific radioactivity—time curves in terms of a two-compartment system indicated that all the cholesterol of muscle is exchangeable with the plasma cholesterol and that local synthesis does not contribute significantly to the cholesterol in muscle. 3. Analysis of the curve for specific radioactivity of skin cholesterol suggested the presence of a small pool of cholesterol with slow turnover. A contribution to skin cholesterol from local synthesis could not be excluded.

scholarly journals Loss of haem in rat liver caused by the porphyrogenic agent 2-allyl-2-isopropylacetamide

1971 ◽  
Vol 124 (4) ◽  
pp. 767-777 ◽  
Author(s):  
F. De Matteis
Keyword(s):  
Rat Liver ◽  
Microsomal Fraction ◽  
Direct Evidence ◽  
Gradual Increase ◽  
Rapid Loss ◽  
Metabolizing Enzymes ◽  
Liver Microsomal Fraction ◽  
Green Pigments ◽  
Cytochrome P 450 ◽  
Increased Activity

1. The effect of a single dose of 2-allyl-2-isopropylacetamide on the cytochrome P-450 concentration in rat liver microsomal fraction was studied. The drug caused a rapid loss of cytochrome P-450 followed by a gradual increase to above the normal concentration. 2. The loss of cytochrome P-450 was accompanied by a loss of microsomal haem and by a brown–green discoloration of the microsomal fraction suggesting that a change in the chemical constitution of the lost haem had taken place. Direct evidence for this was obtained by prelabelling the liver haems with radioactive 5-aminolaevulate: the drug caused a loss of radioactivity from the haem with an increase of radioactivity in a fraction containing certain un-identified green pigments. 3. Evidence was obtained by a dual-isotopic procedure that rapidly turning-over haem(s) may be preferentially affected. 4. The loss of cytochrome P-450 as well as the loss of microsomal haem and the discoloration of the microsomal fraction were more intense in animals pretreated with phenobarbitone and were much less evident when compound SKF 525-A (2-diethylaminoethyl 3,3-diphenylpropylacetate) was given before 2-allyl-2-isopropylacetamide, suggesting that the activity of the drug-metabolizing enzymes may be involved in these effects. 5. The relevance of the destruction of liver haem to the increased activity of 5-aminolaevulate synthetase caused by 2-allyl-2-isopropylacetamide is discussed.

Kinetic analysis of the preserved rat liver by isolated perfusion with ammonium chloride as a load

Life Sciences ◽  
1991 ◽  
Vol 49 (23) ◽  
pp. 1747-1754 ◽  
Author(s):  
Shiro Uyama ◽  
Akira Tanaka ◽  
Koichi Tanaka ◽  
Kazue Ozawa
Keyword(s):  
Kinetic Analysis ◽  
Ammonium Chloride ◽  
Rat Liver ◽  
Isolated Perfusion

scholarly journals Anomeric specificity of d-glucose phosphorylation by rat liver glucose-6-phosphatase

1989 ◽  
Vol 261 (2) ◽  
pp. 509-513
Author(s):  
R Ramirez ◽  
D Zähner ◽  
G Marynissen ◽  
A Sener ◽  
W J Malaisse
Keyword(s):  
Rat Liver ◽  
Glycogen Synthesis ◽  
Liver Microsomes ◽  
Diabetic Rats ◽  
Enzymic Activity ◽  
Rat Liver Microsomes ◽  
Maximal Velocity ◽  
Carbamoyl Phosphate ◽  
Glucose Phosphorylation ◽  
Anomeric Specificity

The anomeric specificity of D-glucose phosphorylation by hepatic glucose-6-phosphatase was examined in rat liver microsomes incubated in the presence of carbamoyl phosphate. At 10 degrees C, the Km for the equilibrated hexose and phosphate donor was close to 56 mM and 11 mM, respectively. The enzymic activity, which was increased in diabetic rats, was about 40% lower in untreated than in sonicated microsomes. No anomeric difference in affinity was found in sonicated microsomes. In untreated microsomes, however, the Km for beta-D-glucose was slightly lower than that for alpha-D-glucose. The maximal velocity was higher with beta- than alpha-D-glucose in both untreated and sonicated microsomes. These data indicate that the phosphotransferase activity of glucose-6-phosphatase cannot account for the higher rate of glycolysis and glycogen synthesis found in hepatocytes exposed to alpha- rather than beta-D-glucose.

scholarly journals The availability of inorganic sulphate in blood for sulphate conjugation of drugs in rat liver in vivo. (35S)Sulphate incorporation into harmol sulphate

1978 ◽  
Vol 172 (2) ◽  
pp. 247-251 ◽  
Author(s):  
G J Mulder ◽  
E Scholtens
Keyword(s):  
Plasma Concentration ◽  
Rat Liver ◽  
Biliary Excretion ◽  
Time Course ◽  
Specific Radioactivity ◽  
Pool Size ◽  
Inorganic Sulphate ◽  
Initial Decrease ◽  
Sulphate Conjugate

1. When Na235SO4 is injected intravenously in rats, it is immediately available for sulphate conjugation of the phenolic drug harmol (7-hydroxyl-1-methyl-9H-pyrido[3,4-b]indole) in the liver. This was established by following the time course of the biliary excretion of the sulphate conjugate of harmol, and the incorporation of [35S]sulphate into harmol sulphate. 2. During the 10min immediately after injection of Na235SO4 re-distribution of [35S]sulphate took place, which resulted in a rapid initial decrease in the plasma concentration of [35S]sulphate; a concomitant decrease in the amount of [35S]sulphate incorporated into harmol sulphate was observed, indicating that the co-substrate of sulphation, adenosine 3′-phosphate 5′-sulphatophosphate, equilibrates rapidly with [35S]sulphate in plasma. 3. The results suggest that the pool size of adenosine 3′-phosphate 5′-sulphatophosphate is very small; therefore the specific radioactivity of [35S]sulphate in plasma determines the specific radioactivity incorporated into sulphate esters at any time.

Kinetic analysis using specific radioactivity data

1986 ◽  
pp. 384-395 ◽  
Author(s):  
Ngoc-Anh Le ◽  
Rajasekhar Ramakrishnan ◽  
Ralph B. Dell ◽  
Henry N. Ginsberg ◽  
W.Virgil Brown
Keyword(s):  
Kinetic Analysis ◽  
Specific Radioactivity
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