Studies on the biological control of glycogen metabolism in liver. III. Subcellular distribution of glycogen metabolizing enzymes

1968 ◽  
Vol 46 (6) ◽  
pp. 521-525 ◽  
Author(s):  
V. T. Maddaiah ◽  
N. B. Madsen
Keyword(s):  
Biological Control ◽  
Subcellular Distribution ◽  
Microsomal Fraction ◽  
Glycogen Metabolism ◽  
Liver Glycogen ◽  
Supernatant Fraction ◽  
Metabolizing Enzymes ◽  
Pellet Fraction ◽  
Fasting And Refeeding ◽  
Microsomal Pellet

In a study of the subcellular distribution of the enzymes of the glycogen cycle in rat liver, glycogen synthetase was found in both the microsomal pellet and supernatant fractions, but the activity was always greater in the pellet than in the supernatant fraction. Variations in the concentration of liver glycogen, brought about by fasting and refeeding, did not alter this distribution. In agreement with the results of others, phosphorylase appeared almost entirely in the microsomal fraction, presumably bound to glycogen, when liver glycogen was high, or in the supernatant fraction when liver glycogen was low. These results indicate that synthetase and phosphorylase may be bound with different affinities or to different forms of glycogen.Regardless of whether the animals were fasted or fed, significant amounts of UDPG pyrophosphorylase activity appeared in the microsomal pellet fraction. The remainder of UDPG pyrophosphorylase and all of phosphoglucomutase activities were present in the microsomal supernatant fraction. As synthetase and phosphorylase are bound to glycogen, which in turn is known to be associated with the endoplasmic reticulum, the occurrence of UDPG pyrophosphorylase, synthetase, and phosphorylase in the microsomal fraction may have functional significance to the glycogen cycle.

scholarly journals The subcellular distribution of copper, zinc and iron in liver and kidney. Changes during copper deficiency in the rat

1974 ◽  
Vol 32 (2) ◽  
pp. 435-445 ◽  
Author(s):  
Begoña Alfaro ◽  
F. W. Heaton
Keyword(s):  
Subcellular Distribution ◽  
Copper Deficiency ◽  
Microsomal Fraction ◽  
Supernatant Fraction ◽  
Molecular Weights ◽  
Cu Deficiency ◽  
Fe Content ◽  
Liver And Kidney ◽  
Copper Zinc ◽  
And Control

1. The subcellular distribution of copper, zinc and iron was investigated in liver and kidney homogenates from Cu-deficient and control rats. The supernatant fraction contained most Cu and Zn in control animals, but the highest proportion of Fe was in the microsomal fraction.2. Cu deficiency reduced the concentration of the metal in all fractions, but the depletion was most severe and developed most rapidly in the supernatant fraction, indicating that the soluble cytoplasm is the site of Cu storage in the cell. The Fe content of the liver increased during Cu deficiency with Fe being deposited preferentially in the mitochondria.3. All the Cu and most of the Zn in liver and kidney supernatant fractions occurred in four protein-containing fractions that were of similar molecular weights in both organs. A fraction of molecular weight 30000 was primarily concerned with Cu storage in mature rats.4. The reduction in liver Zn during Cu deficiency appeared to be the result of impaired intestinal absorption and it is suggested that a small amount of Cu facilitates the absorption of Zn.

INCORPORATION OF IODIDE INTO ORGANIC COMPOUNDS IN THE GUINEA PIG THYROID

1963 ◽  
Vol 43 (1) ◽  
pp. 110-118 ◽  
Author(s):  
R. Ekholm ◽  
T. Zelander ◽  
P.-S. Agrell
Keyword(s):  
Guinea Pig ◽  
Protein Binding ◽  
Organic Compounds ◽  
Guinea Pigs ◽  
Microsomal Fraction ◽  
Thyroid Tissue ◽  
Particulate Fraction ◽  
Supernatant Fraction ◽  
Hydrolysis Of

ABSTRACT Guinea pigs, kept on a iodine-sufficient diet, were injected with Na131I and the thyroids excised from 45 seconds to 5 days later. The thyroid tissue was homogenized and separated into a combined nuclear-mitochondrial-microsomal fraction and a supernatant fraction by centrifugation at 140 000 g for one hour. Protein bound 131iodine (PB131I) and free 131iodide were determined in the fractions and the PB131I was analysed for monoiodotyrosine (MIT), diiodotyrosine (DIT) and thyroxine after hydrolysis of PB131I. As early as only 20 minutes after the Na131I-injection almost 100% of the particulate fraction 131I was protein bound. In the supernatant fraction the protein binding was somewhat less rapid and PB131I values above 90% of total supernatant 131I were not found until 3 hours after the injection. In all experiments the total amount of PB131I was higher in the supernatant than in the corresponding particulate fraction. The ratio between supernatant PB131I and pellet PB131I was lower in experiments up to 3 minutes and from 2 to 5 days than in experiments of 6 minutes to 20 hours. Hydrolysis of PB131I yielded, even in the shortest experiments, both MIT and DIT. The DIT/MIT ratio was lower in the experiments up to 2 hours than in those of 3 hours and over.

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.

Biosynthesis of Nitrogenous Phospholipids in Spinach Leaves

1974 ◽  
Vol 52 (6) ◽  
pp. 469-482 ◽  
Author(s):  
M. O. Marshall ◽  
M. Kates
Keyword(s):  
Microsomal Fraction ◽  
Enzyme System ◽  
Supernatant Fraction ◽  
Exchange Reactions ◽  
Methylation Pathway ◽  
Ethanolamine Kinase ◽  
Spinach Leaves

Pathways for biosynthesis of phosphatidylserine (PS), phosphatidylethanolamine (PE), and phosphatidylcholine (PC), in spinach leaves have been studied both in vivo (whole leaves and leaf slices) and in vitro (cell-free leaf fractions). Biosynthesis of PS was shown to occur by the action of a particle-bound CDP-diglyceride: serine phosphatidyltransferase, and PE by the action of a PS-decarboxylase localized in the 100 000 × g supernatant fraction. PE was also formed by the operation of the CDP-ethanolamine:diglyceride phosphorylethanolamine transferase, localized in the microsomal fraction. The presence of ethanolamine kinase required for formation of phosphorylethanolamine was demonstrated in vitro, but not the presence of CTP:phosphorylethanolamine cytidyltransferase; however, the latter is presumed present on the basis of in vivo results. Operation of the methylation pathway for biosynthesis of PC was established in vivo, and direct methylation of phosphatidyl-N-methylethanolamine to phosphatidyl-N,N-dimethylethanolamine (PE-diMe) and of PE-diME to PC by S-adenosylmethionine was demonstrated with a particulate enzyme system localized in the microsomal fraction; direct methylation of PE itself could not be shown in this system. PC was also synthesized by the CDP-choline:diglyceride phosphorylcholine transferase system localized in the microsomal fraction. Synthesis of PE and PC by Ca2+-stimulated exchange reactions with ethanolamine and choline, respectively, could be demonstrated, but at low rates. However, no synthesis of PS by exchange reactions with serine could be detected.

THE BIOLOGICAL CONTROL OF GLYCOGEN METABOLISM IN AGROBACTERIUM TUMEFACIENS

1963 ◽  
Vol 41 (1) ◽  
pp. 561-571 ◽  
Author(s):  
N. B. Madsen
Keyword(s):  
Biological Control ◽  
Agrobacterium Tumefaciens ◽  
Sharp Decrease ◽  
Glycogen Metabolism ◽  
Exponential Growth Phase ◽  
Lag Phase ◽  
Uridine Diphosphate ◽  
High Positive Correlation ◽  
Growth And Nutrition ◽  
Diphosphate Glucose

The hypothesis has been advanced that the inhibition of phosphorylase by uridine diphosphate glucose (UDPG), together with the fact that the latter compound is the substrate for glycogen synthetase, is the basis of a mechanism for the biological control of glycogen metabolism in Agrobacterium tumefaciens. Experiments were designed to test this hypothesis on the assumption that such a control mechanism would manifest itself by the concentrations of UDPG and glycogen bearing some relationship to each other during various stages of growth and nutrition. Glycogen levels in the cells increased markedly during the lag phase of growth, decreased during the exponential growth phase, and increased again as growth ceased due to the depletion of nitrogen from the medium (nitrogen starvation). The UDPG concentration paralleled these changes, and a high positive correlation between the concentrations of UDPG and glycogen was demonstrated. The addition of ammonium chloride to nitrogen-starved cells caused a prompt resumption of growth, a sharp decrease in the UDPG concentration, and a somewhat smaller decrease in glycogen concentration. Cells placed in buffered salt solution and aerated had a low concentration of UDPG and exhibited a steady decline of the glycogen reserves. Although factors other than those considered here may also be of importance in the control of glycogen metabolism in this organism, the data in general support the hypothesis advanced above.

Effect of estradiol on tissue glycogen metabolism and lipid availability in exercised male rats

1991 ◽  
Vol 71 (5) ◽  
pp. 1694-1699 ◽  
Author(s):  
Z. V. Kendrick ◽  
G. S. Ellis
Keyword(s):  
Fatty Acids ◽  
Body Weight ◽  
Exercise Performance ◽  
Glycogen Content ◽  
Day Treatment ◽  
Glycogen Metabolism ◽  
Liver Glycogen ◽  
Male Rats ◽  
Plasma Lactate ◽  
Glycogen Utilization

The effect of 17 beta-estradiol 3-benzoate (10 micrograms.0.1 ml sunflower oil-1.100 g body wt-1) on exercise performance, tissue glycogen utilization, and lipid availability was determined in male rats. In experiment 1, estradiol or oil was administered 1 h or 1–6 days before a treadmill run to exhaustion. No differences in body weight between oil- and estradiol-administered animals were observed during the 6-day treatment. Animals receiving estradiol for 3–6 days ran significantly longer and completed more work than oil-administered animals. Significant degradation of red and white vastus muscle, myocardial, and liver glycogen was observed in all animals run to exhaustion. In experiment 2, animals were administered estradiol for 5 days and then run for 2 h. The submaximal run for 2 h significantly reduced tissue glycogen content in red and white vastus muscle, heart, and liver of oil-administered animals. The latter effect was attenuated in both vastus muscles, liver, and myocardial tissues in the estradiol-administered animals. Estradiol administration significantly increased plasma fatty acids and lowered plasma lactate during the submaximal run. These data indicate that when body weight remained constant between groups of male rats, estradiol administration for 3–6 days increased exercise performance. Furthermore, estradiol administration for 5 days resulted in greater lipid availability and less tissue glycogen utilization during submaximal running for 2 h.

Monoacylglycerol lipase activity in cardiac myocytes

1988 ◽  
Vol 66 (9) ◽  
pp. 1013-1018 ◽  
Author(s):  
David L. Severson ◽  
Mariette Hee-Cheong
Keyword(s):  
Lipase Activity ◽  
Competitive Inhibitor ◽  
Product Inhibition ◽  
Fatty Acyl ◽  
Supernatant Fraction ◽  
Monoacylglycerol Lipase ◽  
Pellet Fraction ◽  
Rat Hearts ◽  
Triton X ◽  
Hydrolysis Of

Monoacylglycerol lipase activity in homogenates of isolated myocardial cells (myocytes) from rat hearts was recovered in both particulate and soluble subcellular fractions. The activity present in the microsomal (100 000 × g pellet) fraction was solubilized by treatment with Triton X-100 and combined with the 100 000 × g supernatant fraction; the properties of monoacylglycerol lipase were investigated with this soluble enzyme preparation. The Km for the hydrolysis of a 2-monoolein substrate was 16 μM. The rates of hydrolysis of 1-monoolein and 2-monoolein were identical, and 1-monoolein was a competitive inhibitor (Ki = 20 μM) of the hydrolysis of 2-monoolein. Monoacylglycerol lipase activity was regulated by product inhibition according to the following order of potency: fatty acyl CoA > free fatty acids > fatty acyl carnitine.

Potassium-stimulated 45Ca2+ uptake by subcellular particles of pancreatic beta-cells

1981 ◽  
Vol 240 (1) ◽  
pp. C35-C38 ◽  
Author(s):  
J. Sehlin
Keyword(s):  
Ionic Strength ◽  
Beta Cells ◽  
Calcium Ions ◽  
Subcellular Distribution ◽  
Pancreatic Beta Cells ◽  
Microsomal Fraction ◽  
Maximum Effect ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Mouse Islets

Accumulation of 45Ca2+ by a microsomal fraction from pancreatic beta-cells of obese-hyperglycemic (ob/ob) mice was stimulated by Mg2+ in a concentration-dependent manner when 2 mM ATP was present. Maximum effect was reached at 2 mM Mg2+. Increasing the Na+ concentration from 20 to 115 mM had no significant effect, but K+ (10-123 mM) stimulated 45Ca2+ accumulation markedly when tested in the presence of 2 mM Mg2+. This effect was not due to changes of osmolarity, ionic strength, or the concentration of Cl-. Stimulation by K+ was drastically reduced on omission of Mg2+ from the incubation medium. K+ did not significantly affect 45Ca2+ uptake by a mitochondria-rich fraction of ob/ob mouse islets. It is suggested that K+ may be involved in modifying the subcellular distribution of calcium ions in pancreatic beta-cells.

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