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At least 613 records · Page 34Linked to original sources
PubMed1985

The effect of streptozotocin-induced diabetes on hepatic hexose transport.

3-O-methyl-D-glucose (which is not metabolized in isolated parenchymal cells) was used to characterize the hexose transport process in hepatocytes prepared from 24 h fasted rats. The Vmax and Km obtained were 161 +/- 12 nmol/mg dry wt./min and 39 +/- 4 mM respectively (Europe-Finner GN, 1984, Biosci. Rep. 4, 483-489). Streptozotocin-induced diabetes decreased the Km of the system by 50% to a value of 19 +/- 6 mM without causing any change in the Vmax. Short term insulin treatment of cells prepared from 24 h diabetic rats appeared to partially return the system to normal.

3-O-Methylglucose↗
PubMed1981

Stimulation of neutrophil chemotaxis, adhesiveness, phagocytosis, and hexose monophosphate shunt activity by N-(2-mercaptopropionyl)glycine.

The effects of the sulfydryl donor drug N-(2-mercaptopropionyl)-glycine (MPG) on neutrophil chemotaxis, adhesiveness, phagocytosis, and hexose monophosphate shunt activity were investigated in vitro. The drug significantly enhanced all the neutrophil functions tested when used at appropriate concentrations. The results, which are in accord with the well known inhibition of neutrophil function by sulfydryl-blocking agents, suggest the possible therapeutic usefulness of the drug in clinical conditions with defective neutrophil function.

Amino Acids, Sulfur↗
PubMed1990

Decreased cell proliferation and PGE2 production by fibroblasts treated with a modified hexose sugar, amiprilose hydrochloride.

Amiprilose hydrochloride, a modified hexose sugar effectively decreases proliferation of human skin and synovial fibroblasts and of rabbit synovial fibroblasts. It also decreases production of the inflammatory mediator prostaglandin E2 (PGE2) by these cells. Cell proliferation, measured by incorporation of 3H-thymidine and by cell number, is decreased by concentrations of amiprilose hydrochloride of 1 mg/ml, while PGE2 synthesis is decreased by concentrations as low as 10 micrograms/ml. Concentrations of 1 mg/ml are not cytotoxic, as measured by protein synthesis. The anti-proliferate and anti-inflammatory effects of amiprilose hydrochloride, combined with its lack of cytotoxicity, suggest that this compound may be useful in the treatment of rheumatoid arthritis, a chronic autoimmune proliferate and inflammatory disease of connective tissue.

Animals↗
PubMedDate not supplied

Significance of the hexose monophosphate shunt in experimentally induced cardiac hypertrophy.

1. In three models of cardiac hypertrophy in rats (aortic constriction, application of a single dose of isoproterenol and daily injections of triiodothyronine) the biosynthesis of myocardial adenine nucleotides was enhanced. 2. In hypertrophying hearts due to aortic constriction and isoproterenol application, the activity of glucose-6-phosphate dehydrogenase and the available pool of 5-phosphoribosyl-1-pyrophosphate were increased indicating a stimulation of the hexose monophosphate shunt. In triiodothyronine-treated animals only the cardiac pool of 5-phosphoribosyl-1-pyrophosphate turned out to be elevated. 3. In all three models of cardiac hypertrophy, the enhancement of myocardial adenine nucleotide biosynthesis was exaggerated by ribose. It thus appears that the 5-phosphoribosyl-1-pyrophosphate pool is the limiting factor for the increase of adenine nucleotide biosynthesis under these conditions. 4. Long-term i.v. infusion of ribose (200 mg/kg/h) in isoproterenol-treated rats prevented the decrease of the cardiac ATP concentration induced by isoproterenol. However, the isoproterenol-induced stimulation of total cardiac protein synthesis was not altered, suggesting that the ATP decline may not be the trigger for stimulating protein synthesis in this model of myocardial hypertrophy.

Adenine Nucleotides↗
PubMed1979

Morphogenic effect of 2-deoxy-D-arabino-hexose on Rhodosporidium toruloides.

The presence of 2-deoxy-D-arabino-hexose in the growth medium caused marked morphological changes in the cells of Rhodosporidium toruloides. The originally elongated ellipsoidal cells grew spherically in the presence of the deoxy-sugar, displayed differences in cell division and separation, and were larger than the control cells. After exhaustion of glucose from the medium the cells died, although no lysis was observed. The morphological changes were accompanied by significant alterations in the carbohydrate composition of the cell wall. The wall of R. toruloides grown in the presence of the deoxy-sugar contains higher proportions of chitin and glucan, while the relative contents of mannose and galactose polymers decreased drastically in comparison to normal cells.

Basidiomycota↗
PubMed2002

Activation of the hexose monophosphate shunt in rat type II pneumocytes as an early marker of oxidative stress caused by cobalt particles.

Cobalt metal (mCo) and hard metal, a mixture of cobalt and tungsten carbide (CoWC), are cytotoxic for alveolar macrophages and alveolar type II cells (AT-II). Although the exact mechanisms of toxicity are not entirely elucidated, evidence exists for an oxidant-mediated toxicity. In this study, we exposed primary cultures of rat AT-II, in vitro, to different forms of cobalt (mCo particles, CoWC particles, CoCl(2)) and assessed changes in the activity of the hexose monophosphate shunt (HMS). Activation of the HMS occurs as an early response to (per)oxidative stress. Cobalt metal-containing particles (mCo and CoWC) when freshly immersed in medium, lead to an early concentration-dependent stimulation of the HMS in rat AT-II. The maximum stimulations of HMS (reached after 90 min) were 2.0 +/-1.2, 2.9+/-0.4, 3.3 +/-1.6 and 4.0+/-0.4 fold-increases for 15, 75, 300 and 1200 microg mCo/well, respectively. The observed time course of the activation by mCo particles clearly differed from that caused by paraquat (10(-5 )M), which is known to produce activated oxygen species after cyclic oxidation-reduction reactions. The comparable effect of peroxides (H2O2 and t-butyl hydroperoxide) on HMS and the inhibitory effects of catalase on the mCo-induced stimulation of the HMS strongly suggest the production of peroxides by freshly immersed mCo particles. However, we were not able to show a simple relationship between the stimulation of the HMS and the subsequent cell damage.

Animals↗
PubMed2003

Hexose monophosphate shunt activities in human erythrocytes during oxidative damage induced by hydrogen peroxide.

Human red blood cells (HRBCs) were exposed to H(2)O(2) either as bolus or as a flux generated by a glucose-glucose oxidase system. H(2)O(2) concentrations were in the range 10(-5)-10(-3) M and exposure times to the oxidative stress were 10 min and 60 min. The production of NADPH by the hexose monophosphate shunt (HMPS) was accurately measured by gas chromatography-isotope ratio mass spectrometry as the production of (13)CO(2) from [1-(13)C]glucose. Depending on the duration of exposure and H(2)O(2) concentration, the production of (13)CO(2) by HRBCs under a flux of H(2)O(2) was increased two- to eight-fold in comparison with that obtained under a bolus of H(2)O(2). Under flux stimulation, spectral data show the formation of compound I, and a red shift caused by the presence of compounds II and III, whereas under a bolus stress no obvious spectra changes were observed. Inhibition of catalase by 3-amino-1,2,4-triazole (3-AT) or by sodium azide, followed by a bolus of H(2)O(2) led to a two- to five-fold increases in (13)CO(2) production compared with controls, depending on H(2)O(2) concentration. In contrast, 3-AT-inhibited HRBCs exposed to a flux of H(2)O(2) did not present an increase in (13)CO(2) production. The present paper emphasizes the importance and role of NADPH production following a bolus or a flux stimulation of H(2)O(2). The difference between responses in HMPS activities under the two types of stress could be related to a different balance of activity between 'catalatic' and 'peroxidatic' modes of catalase following H(2)O(2) exposure.

Carbon Dioxide↗
PubMed2005

Active hexose correlated compound enhances tumor surveillance through regulating both innate and adaptive immune responses.

Active hexose correlated compound (AHCC) is a mixture of polysaccharides, amino acids, lipids and minerals derived from cocultured mycelia of several species of Basidiomycete mushrooms. AHCC has been implicated to modulate immune functions and plays a protective role against infection. However, the potential role of AHCC in tumor immune surveillance is unknown. In this study, C57BL/6 mice were orally administered AHCC or water, followed by tumor cell inoculation. We showed that compared to pure water-treated mice, AHCC treatment significantly delayed tumor development after inoculation of either melanoma cell line B16F0 or lymphoma cell line EL4. Treatment with AHCC enhanced both Ag-specific activation and proliferation of CD4(+) and CD8(+) T cells, increased the number of tumor Ag-specific CD8(+) T cells, and more importantly, increased the frequency of tumor Ag-specific IFN-gamma producing CD8(+) T cells. Interestingly, AHCC treatment also showed increased cell number of NK and gammadelta T cells, indicating the role of AHCC in activating these innate-like lymphocytes. In summary, our results demonstrate that AHCC can enhance tumor immune surveillance through regulating both innate and adaptive immune responses.

Animals↗
PubMed2002

Expression during rat fetal development of GLUT12--a member of the class III hexose transporter family.

Glucose is an essential molecule for most mammalian cells, and is particularly important during fetal development, when cells are rapidly dividing and differentiating. In rats, GLUT1 is present at high levels in most fetal tissues, with levels decreasing after birth. We used immunohistochemistry to localise GLUT12 protein, a recently identified member of the sugar transporter family, and GLUT1 during rat fetal development. GLUT12 staining was observed in heart muscle from gestational days 15 to 21. GLUT12 staining in skeletal muscle increased from gestational days 17 to 21, and GLUT12 was also detected in brown adipose tissue. The expression of GLUT12 in insulin-responsive tissues supports a potential role for GLUT12 in the provision of glucose to these tissues before the appearance of GLUT4. GLUT12 protein was also expressed in fetal chondrocytes from gestational day 15 onward, in kidney distal tubules and collecting ducts from day 19, and in lung bronchioles from day 19. The specific pattern of expression observed in the rat fetus suggests that GLUT12 may be important in hexose delivery to developing tissues.

Animals↗
PubMed1980

Urinary acidification in a patient with glucose-6-phosphate dehydrogenase deficiency. A reevaluation of the role of the hexose monophosphate shunt in renal acid secretion.

The relationship between renal metabolism and urinary acidification is poorly understood. During the past decade evidence has accrued to suggest that the hexose monophosphate (HMP) shunt might serve in the process of urinary acidification by providing reducing equivalents for a redox-coupled membrane-bound proton pump that could transport protons into the tubular lumen. The major support for this hypothesis has come from the finding that HMP shunt activity increases with acute and chronic metabolic acidosis. In the present study, we examine the urinary acidification capacity of a young man with severe erythrocyte glucose-6-phosphate dehydrogenase (G-6-PD) deficiency and with unmeasurable G-6-PD activity in renal cortical tissue. We found that despite unmeasurable G-6-PD activity in renal tissue, the patient was capable of generating a maximally acid urine and increasing total acid secretion. Our findings suggest that the HMP shunt may not be necessary for the urinary acidification process.

Adolescent↗
PubMed1990

Hexose monophosphate shunt measurement in cultured cells with [1-13C]glucose: correction for endogenous carbon sources using [6-13C] glucose.

Hexose monophosphate shunt (HMPS) activity can be measured with 1H nuclear magnetic resonance spectroscopy or gas chromatography--mass spectrometry by monitoring the differential production of [3-13C]lactate and [3-12C]lactate from the degradation of [1-13C]-glucose. Errors in measurement of HMPS activity can arise from unlabeled lactate precursors, by recycling of HMPS products, and by incomplete fractional enrichment of labeled glucose. A method utilizing cultured cells incubated with [1-13C]glucose in parallel with incubations using [6-13C]glucose to correct for all these problems is presented. In cultured rat C6 glioma and 9L gliosarcoma cells, failure to apply this correction results in an approximately twofold overestimation of HMPS activity.

Animals↗
PubMed1985

Hexose monophosphate shunt-stimulated reduction of methemoglobin by divicine.

Reduced divicine (2,6-diamino-4,5-dihydroxypyrimidine), an aglycone implicated in the pathogenesis of favism, reduces methemoglobin efficiently in intact erythrocytes and in hemolysates. Oxidized divicine produces the same effect when glucose or an NADPH-generating system is added to intact erythrocytes or to hemolysates. Although NADPH, NADH, and GSH have no direct methemoglobin-reducing activity in vitro, they convert oxidized divicine to the reduced hydroquinone species, which is responsible for the electron transfer to methemoglobin. Reduction of methemoglobin is optimally observed under nitrogen since, in the presence of oxygen, reduced divicine undergoes autoxidation. Several lines of evidence rule out the reduction of methemoglobin by divicine through an enzyme-catalyzed process, although it is certainly sustained by the hexose monophosphate shunt activity of erythrocytes through the generation of both NADPH and GSH. Thus, the strong enhancing effect that glucose produces on the divicine-dependent methemoglobin reduction within intact normal erythrocytes is completely absent in erythrocytes from glucose-6-phosphate dehydrogenase-deficient subjects. This distinctive behavior might account for the enhanced methemoglobin levels that are found both in vitro in glucose-6-phosphate dehydrogenase-deficient erythrocytes exposed to divicine and in vivo as a typical feature of the acute hemolytic crisis of favic patients.

Catalase↗
PubMed1992

Hexose metabolism in pancreatic islets: unequal oxidation of the two carbons of glucose-derived acetyl residues.

The fate of the C1 and C2 of glucose-derived acetyl residues was examined in rat pancreatic islets. The production of 14CO2 from D-[2-14C]glucose exceeded that from D-[6-14C]glucose, in the same manner as the oxidation of [1-14C]acetate exceeded that of [2-14C]acetate. The difference in 14CO2 output from D-[2-14C]glucose and D-[6-14C]glucose was matched by complementary differences in the generation of 14C-labeled acidic metabolites and amino acids. Even the production of 14C-labeled L-lactate was somewhat higher in the case of D-[6-14C]glucose than D-[2-14C]glucose. The ratio between D-[2-14C]glucose and D-[6-14C]glucose oxidation progressively decreased at increasing concentrations of the hexose (2.8, 7.0, and 16.7 mM), was higher after 30 than 120 min incubation, and was decreased in the presence of a nonmetabolized analogue of L-leucine. These findings are consistent with the view that the difference between D-[6-14C]glucose and D-[2-14C]glucose oxidation is mainly attributable to the inflow into the Krebs cycle of unlabeled metabolites generated from endogenous nutrients, this being compensated by the exit of partially labeled metabolites from the same cycle. The present results also indicate that the oxidation of glucose-derived acetyl residues relative to their generation in the reaction catalyzed by pyruvate dehydrogenase is higher than that estimated from the ratio between D-[6-14C]glucose and D-[3,4-14C]glucose conversion to 14CO2.

Acetates↗
PubMed1987

Binding of cytochalasin B to trypsin and thermolysin fragments of the human erythrocyte hexose transporter.

The cleavage of the human erythrocyte hexose transporter by the proteinases trypsin and thermolysin has been studied. When red cell membranes are treated with trypsin, washed and then photolabelled with cytochalasin B, a labelled peak at 18 kDa is obtained. This labelling of the cleaved transporter is D-glucose inhibitable. This probably indicates that the residual 36 kDa portion of the transporter is not required for binding of ligands. Extensive cleavage of the transporter with low concentrations of thermolysin only occurs when transporter is prelabelled with cytochalasin B. This indicates that covalently bound cytochalasin B can cause a conformational change which exposes the thermolysin cleavage site.

Binding Sites↗
PubMed1991

Sodium-dependent phosphate and alanine transports but sodium-independent hexose transport in type II alveolar epithelial cells in primary culture.

Inorganic phosphate, amino acids and sugars are of obvious importance in lung metabolism. We investigated sodium-coupled transports with these organic and inorganic substrates in type II alveolar epithelial cells from adult rat after one day in culture. Alveolar type II cells actively transported inorganic phosphate and alanine, a neutral amino acid, by sodium-dependent processes. Cellular uptakes of phosphate and alanine were decreased by about 80% by external sodium substitution, inhibited by ouabain (30 and 41%, respectively) and displayed saturable kinetics. Two sodium-phosphate cotransport systems were characterized: a high-affinity one (apparent Km = 18 microM) with a Vmax of 13.5 nmol/mg protein per 10 min and a low-affinity one (apparent Km = 126 microM) with a Vmax of 22.5 nmol/mg protein per 10 min. Alanine transport had an apparent Km of 87.9 microM and a Vmax of 43.5 nmol/mg protein per 10 min. By contrast, cultured alveolar type II cells did not express sodium-dependent hexose transport. Increasing time in culture decreased Vmax values of the two phosphate transport systems on day 4 while sodium-dependent alanine uptake was unchanged. This study demonstrated the existence of sodium-dependent phosphate and amino acid transports in alveolar type II cells similar to those documented in other epithelial cell types. These sodium-coupled transports provide a potent mechanism for phosphate and amino acid absorption and are likely to play a role in substrate availability for cellular metabolism and in regulating the composition of the alveolar subphase. The decrease in phosphate uptake with time in culture is parallel to decrease in surfactant synthesis reported in cultured alveolar type II cells, suggesting that phosphate availability for surfactant synthesis may be accomplished by a sodium-dependent phosphate uptake.

Alanine↗
PubMed1978

Intramembraneous localization of rat liver microsomal hexose-6-phosphate dehydrogenase and membrane permeability to its substrates.

A method for purifying hexose-6-phosphate dehydrogenase (beta-D-glucose: NAD(P) -oxidoreductase, EC 1.1.1.47) from rat liver microsomes is described. The purified enzyme was shown to be homogeneous by sodium dodecyl sulfate (SDS)-polyacrylamide electrophoresis. It is shown that the enzyme is bound to the inner surface of microsomal membranes, and that glucose 6-phosphate, but not NADP, penetrates almost freely into the membranes at 37 degrees C.

Animals↗