Transport as a rate limiting step in glucose metabolism in virus-transformed cells: Studies with cytochalasin B

Human skin fibroblasts from ‘normal’ subjects were found to possess at least two hexose transport systems. One system was responsible for the uptake of 2-deoxy-D-glucose (dGlc), D-glucose and D-galactose, whereas the other was responsible primarily for the uptake of 3-O-methyl-D-glucose (MeGlc). The transport of dGlc was the rate-limiting step in the uptake process; over 97% of the internalized dGlc was phosphorylated and the specific activity of hexokinase was several times higher than that for dGlc transport. The dGlc transport system was activated by glucose starvation, and was very sensitive to inhibition by cytochalasin B and energy uncouplers. Fibroblasts isolated from a patient with symptoms of hypoglycaemia were found to differ from their normal counterparts in the dGlc transport system. They exhibited a much higher transport affinity for dGlc, D-glucose and D-galactose, with no change in the respective transport capacity. Transport was not the rate-limiting step in dGlc uptake by these cells. Moreover, the patient's dGlc transport system was no longer sensitive to inhibition by cytochalasin B and energy uncouplers. This suggested that the intrinsic properties of the patient's dGlc transport system were altered. It should be noted that the patient's dGlc transport system could still be activated by glucose starvation. Despite the changes in the dGlc transport system, the MeGlc transport system in the patient's fibroblasts remained unaltered. The observed difference in the properties of the two hexose transport systems in the ‘normal’ and the patient's fibroblasts strongly suggests that the two transport systems may be coded or regulated by different genes. The present finding provides the first genetic evidence from naturally occurring fibroblasts indicating the presence of two different hexose transport systems.

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PROGESTERONE AND INSULIN-RESISTANCE: STUDIES OF PROGESTERONE ACTION ON GLUCOSE TRANSPORT, LIPOGENESIS AND LIPOLYSIS IN ISOLATED FAT CELLS OF THE FEMALE RAT

Journal of Endocrinology ◽

10.1677/joe.0.0880455 ◽

1981 ◽

Vol 88 (3) ◽

pp. 455-462 ◽

Cited By ~ 22

Author(s):

M.-TH. SUTTER-DUB ◽

B. DAZEY ◽

E. HAMDAN ◽

M.-TH. VERGNAUD

Keyword(s):

Glucose Metabolism ◽

Pentose Phosphate ◽

Fat Cells ◽

Female Rat ◽

Fat Cell ◽

Rate Limiting Step ◽

Limiting Step ◽

Glucose Phosphorylation ◽

Rate Limiting

The effects of progesterone on isolated rat adipocytes were studied in vitro during various steps of glucose metabolism, transport, lipogenesis and lipolysis. Progesterone decreased the phosphorylation of glucose into glucose-6-phosphate as assessed by measuring the uptake of 2-deoxyglucose but it had no effect on transmembrane transport of glucose as determined by measuring the entry of 3-0-methylglucose into the cell. As glucose phosphorylation is a rate-limiting step of the pentose-phosphate pathway, these data could explain the inhibition of lipogenesis and the enhancement of lipolysis observed when progesterone is present in incubation medium. Progesterone might thus modulate a regulatory step of glucose metabolism and antagonize insulin action in the fat cell.

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Transport of fluorescein in trichomes of Lycopersicon esculentum

Canadian Journal of Botany ◽

10.1139/b82-055 ◽

1982 ◽

Vol 60 (4) ◽

pp. 397-402 ◽

Cited By ~ 26

Author(s):

Gregor F. Barclay ◽

Carol A. Peterson ◽

Melvin T. Tyree

Keyword(s):

Lycopersicon Esculentum ◽

Cytoplasmic Streaming ◽

Cytochalasin B ◽

The Other ◽

Square Root ◽

Inhibiting Effect ◽

Rate Limiting Step ◽

Limiting Step ◽

Other Hand ◽

Rate Limiting

Translocation of the dye disodium fluorescein (uranin) in trichomes of Lycopersicon esculentum (tomato) was nonpolar and proportional to the square root of time. Inhibition of cytoplasmic streaming by cytochalasin B had no effect on the rate of dye movement. On the other hand, disruption of plasmodesmatal connections between adjacent cells by plasmolysis strongly diminished the rate of fluorescein translocation. Subsequent deplasmolysis of the cells did not remove the inhibiting effect of plasmolysis. The data are consistent with the interpretation that dye movement proceeds by diffusion, the rate-limiting step being transport through plasmodesmatal connections.

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Monosaccharide transport into lactating-rat mammary acini

Biochemical Journal ◽

10.1042/bj2040493 ◽

1982 ◽

Vol 204 (2) ◽

pp. 493-501 ◽

Cited By ~ 23

Author(s):

L C Threadgold ◽

H G Coore ◽

N J Kuhn

Keyword(s):

Plasma Membrane ◽

Cytochalasin B ◽

Rate Limiting Step ◽

Limiting Step ◽

Monosaccharide Transport ◽

Rat Mammary Gland ◽

The Mean ◽

Rate Limiting ◽

Rate Of Consumption ◽

Uptake And Release

The uptake and release of 3-O-methyl-D-[3H]glucose at 37 degrees C by acini, prepared from lactating-rat mammary gland with collagenase, was inhibited by glucose, phloretin, cytochalasin B, HgCl2 and low temperature. Uptake and phosphorylation of 2-deoxy-D-[3H]glucose, studied in greater detail, could be ascribed to a specific, saturable, inhibitable, process of apparent Km 16 mM and Vmax. approx. 56 nmol/min per mg of protein, plus a non-specific, non-inhibitable process that was monitored with [14C]fructose. The mean rate of uptake of 5 mM-2-deoxyglucose (16 nmol/min per mg of protein) was similar to the rate of consumption of 5 mM-glucose, suggesting that transport was a rate-limiting step in the overall metabolism of glucose. This accords with evidence for a glucose gradient across the plasma membrane.

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Product Release is Not the Rate-Limiting Step during Cytochalasin B-Induced ATPase Activity of Monomeric Actin

Zeitschrift für Naturforschung C ◽

10.1515/znc-1991-1-222 ◽

1991 ◽

Vol 46 (1-2) ◽

pp. 139-144 ◽

Cited By ~ 1

Author(s):

Peter Dancker ◽

Lore Hess ◽

Karl Ritter

Keyword(s):

Steady State ◽

Atpase Activity ◽

Rate Constant ◽

Cytochalasin B ◽

Single Turnover ◽

Rate Limiting Step ◽

Hydrolysis Products ◽

Limiting Step ◽

Rate Limiting ◽

Hydrolysis Of

Abstract Under conditions where cytochalasin B induces ATPase activity of monomeric actin (0.3 mᴍ MgCl2, 1 mᴍ EGTA , 30 (μᴍ cytochalasin B, 1 mᴍ ATP) the rate constant of the exchange of actin-bound ε-ATP for free ATP is about 4 -6 times faster than steady state ATPase activity. When a stoichiometric ATP -actin complex is extracted with PCA (single turnover experiment) the apparent rate constant of Pi generation is not faster than steady state ATPase activity. -The experiments suggest that the hydrolysis of actin-bound ATP and not the subsequent release of hydrolysis products is rate-limiting during cytochalasin-induced ATPase activity of actin.

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Solid products and rate-limiting step in the thermal half decomposition of natural dolomite in a CO2(g) atmosphere

Thermochimica Acta ◽

10.1016/s0040-6031(02)00603-2 ◽

2003 ◽

Cited By ~ 1

Author(s):

D Beruto

Keyword(s):

Rate Limiting Step ◽

Limiting Step ◽

Rate Limiting

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Ornithine Decarboxylase Activity in Cultured Endothelial Cells Stimulated by Serum, Thrombin and Serotonin

Thrombosis and Haemostasis ◽

10.1055/s-0038-1646709 ◽

1978 ◽

Vol 39 (02) ◽

pp. 496-503 ◽

Cited By ~ 8

Author(s):

P A D’Amore ◽

H B Hechtman ◽

D Shepro

Keyword(s):

Endothelial Cells ◽

Ornithine Decarboxylase ◽

Decarboxylase Activity ◽

Aortic Endothelial Cells ◽

Ornithine Decarboxylase Activity ◽

Rate Limiting Step ◽

Bovine Aortic Endothelial Cells ◽

Limiting Step ◽

Rate Limiting ◽

Serum Serotonin

SummaryOrnithine decarboxylase (ODC) activity, the rate-limiting step in the synthesis of polyamines, can be demonstrated in cultured, bovine, aortic endothelial cells (EC). Serum, serotonin and thrombin produce a rise in ODC activity. The serotonin-induced ODC activity is significantly blocked by imipramine (10-5 M) or Lilly 11 0140 (10-6M). Preincubation of EC with these blockers together almost completely depresses the 5-HT-stimulated ODC activity. These observations suggest a manner by which platelets may maintain EC structural and metabolic soundness.

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