2-Deoxy-D-glucose combined with cisplatin enhances cytotoxicity via metabolic oxidative stress in human head and neck cancer cells

Glucose deprivation has been hypothesized to cause cytotoxicity by inducing metabolic oxidative stress in human cancer cells. The current work tests the hypothesis that 2-deoxy-d-glucose (2DG) combined with cisplatin [cis-diamminedichloroplatinum(II)] can enhance cytotoxicity in human head and neck cancer cells (FaDu) by mechanisms involving oxidative stress. Exposure of FaDu cells to the combination of 2DG and cisplatin resulted in a significant decrease in cell survival when compared with 2DG or cisplatin alone. Treatment with 2DG and cisplatin also caused perturbations in parameters indicative of oxidative stress, including decreased intracellular total glutathione and increased percentage of glutathione disulfide. Simultaneous treatment with the thiol antioxidant N-acetylcysteine (NAC) inhibited parameters indicative of oxidative stress, as well as protected FaDu cells from the cytotoxic effects of cisplatin alone and the combination of 2DG and cisplatin. In addition, polyethylene glycol-conjugated antioxidant enzymes (PEG-superoxide dismutase and PEG-catalase) also protected FaDu cells from 2DG toxicity. An inhibitor of glutathione synthesis, l-buthionine-[S,R]-sulfoximine (BSO), sensitized FaDu cells to the cytotoxic effects of 2DG and cisplatin, and these effects were inhibited by NAC. Furthermore, the combination of 2DG, cisplatin, and BSO significantly increased the percentage of glutathione disulfide, which was also inhibited by NAC. These results support the hypothesis that exposure of human head and neck cancer cells to 2DG combined with cisplatin enhances cytotoxicity via metabolic oxidative stress. These findings provide a strong biochemical rationale for evaluating inhibitors of glucose and hydroperoxide metabolism in combination with cisplatin for the treatment of head and neck cancer.

Genistein-induced apoptosis and autophagocytosis in ovarian cancer cells

OBJECTIVE

Genistein, a naturally occurring isoflavenoid abundant in soy products, has anti-neoplastic activity in multiple tumor types. There are several mechanisms reported for genistein's anti-neoplastic activity. In the present study, we studied the mechanism of genistein-induced cell death in ovarian cancer cells.

METHODS

The effect of genistein on the induction of apoptosis, autophagy, and inhibition of glucose uptake in ovarian cancer cells was determined. The effect of genistein on the expression of phosphorylated Akt was determined by immunoblotting.

RESULTS

Genistein is cytotoxic to ovarian cancer cells. The mechanism of genistein-induced cell death includes both apoptosis and autophagy. Because autophagy is typically an adaptive response to nutrient starvation, we hypothesized that genistein could induce a starvation-like signaling response. We show here that genistein treatment results in caspase-independent cell death with hallmarks of autophagy. Genistein treatment dramatically inhibits glucose uptake in ovarian cancer cells, and methyl pyruvate, a cell-permeable 3-carbon substrate for oxidative phosphorylation and fatty acid synthesis, rescues cells from genistein-induced autophagy. In addition, genistein treatment results in reduced levels of phosphorylated Akt, which may contribute towards a mechanism to limit glucose utilization.

CONCLUSIONS

Most conventional chemotherapeutic agents induce apoptotic cell death. Because genistein can induce both apoptotic and autophagic cell death, it has the potential to circumvent chemoresistance due to alterations in apoptotic signaling.

The involvement of phosphatidylinositol 3-kinase /Akt signaling in high glucose-induced downregulation of GLUT-1 expression in ARPE cells

Glucose transporters have been reported to be associated with the development of diabetic retinopathy. Retinal pigment epithelial cells (RPEs) are believed to play an important role in the pathogenesis of diabetic retinopathy. However, the effect of hyperglycemia on glucose transporters in RPEs and the related signal pathways have not yet been elucidated. Therefore, we examined the effect of high glucose on the glucose transporter 1 in ARPEs and the related signal molecules. In the present study, high glucose decreased 2-deoxyglucose uptake in a time (>2 h) and dose dependent manner. In addition, we found that high glucose downregulated the expression of glucose transporter 1 (GLUT-1). The high glucose-induced downregulation of GLUT-1 was blocked by Wortmanin, LY 294002 (PI-3 kinase inhibitors) and Akt (Akt inhibitor). The high glucose increased stimulation of Akt activation in a time dependent manner. We also investigated the upstream regulator of Akt activation. The high glucose-induced phosphorylation of Akt was blocked by bisindolymaleimide I, H-7, staurosporine (protein kinase C [PKC] inhibitors), vitamin C and catalase (antioxidants). In addition, the high glucose-induced downregulation of GLUT-1 was also blocked by PKC inhibitors and antioxidants. Moreover, high glucose increased lipid peroxide formation, which was prevented by PKC inhibitors. In conclusion, high glucose downregulated GLUT-1 by Akt pathway activation mediated by the PKC-oxidative stress signaling pathway in ARPE cells.

High glucose-induced inhibition of 2-deoxyglucose uptake is mediated by cAMP, protein kinase C, oxidative stress and mitogen-activated protein kinases in mouse embryonic stem cells

Abnormally high glucose levels may play an important role in early embryo development and function. In the present study, we investigated the effect of high glucose on 2-deoxyglucose (2-DG) uptake and its related signalling pathway in mouse embryonic stem (ES) cells. 2. 2-Deoxyglucose uptake was maximally inhibited by 25 mmol/L glucose after 24 h treatment. However, 25 mmol/L mannitol and dextran did not affect 2-DG uptake. Indeed, 25 mmol/L glucose decreased GLUT-1 mRNA and protein levels. The glucose (25 mmol/L)-induced inhibition of 2-DG uptake was blocked by pertussis toxin (a G(i)-protein inhibitor; 2 ng/mL), SQ 22,536 (an adenylate cyclase inhibitor; 10(-6) mol/L) and the protein kinase (PK) A inhibitor myristoylated PKI amide-(14-22) (10(-6) mol/L). Indeed, 25 mmol/L glucose increased intracellular cAMP content. 3. Furthermore, 25 mmol/L glucose-induced inhibition of 2-DG uptake was prevented by 10(-4) mol/L neomycin or 10(-6) mol/L U 73,122 (phospholipase C (PLC) inhibitors) and staurosporine or bisindolylmaleimide I (protein kinase (PK) C inhibitors). At 25 mmol/L, glucose increased translocation of PKC from the cytoplasmic fraction to the membrane fraction. The 25 mmol/L glucose-induced inhibition of 2-DG uptake and GLUT-1 protein levels was blocked by SQ 22,536, bisindolylmaleimide I or combined treatment. In addition, 25 mmol/L glucose increased cellular reactive oxygen species and the glucose-induced inhibition of 2-DG uptake were blocked by the anti-oxidants N-acetylcysteine (NAC; 10(-5) mol/L) or taurine (2 yen 10(-3) mol/L). 4. Glucose (25 mmol/L) activated p38 mitogen-activated protein kinase (MAPK) and p44/42 MAPK. Staurosporine (10(-6) mol/L), NAC (10(-5) mol/L) and PD 98059 (10(-7) mol/L) attenuated the phosphorylation of p44/42 MAPK. Both SB 203580 (a p38 MAPK inhibitor; 10(-7) mol/L) and PD 98059 (a p44/42 MAPK inhibitor; 10(-7) mol/L) blocked 25 mmol/L glucose-induced inhibition of 2-DG uptake. 5. In conclusion, high glucose inhibits 2-DG uptake through cAMP, PLC/PKC, oxidative stress or MAPK in mouse ES cells.

Nelfinavir-induced insulin resistance is associated with impaired plasma membrane recruitment of the PI 3-kinase effectors Akt/PKB and PKC-zeta

AIMS/HYPOTHESIS

Chronic exposure of 3T3-L1 adipocytes to the HIV protease inhibitor nelfinavir induces insulin resistance, recapitulating key metabolic alterations of adipose tissue in the lipodystrophy syndrome induced by these agents. Our goal was to identify the defect in the insulin signal transduction cascade leading to nelfinavir-induced insulin resistance.

METHODS

Fully differentiated 3T3-L1 adipocytes were exposed to 30 micro mol/l nelfinavir for 18 h, after which the amount, the phosphorylation and the localisation of key proteins in the insulin signalling cascade were evaluated.

RESULTS

Insulin-induced interaction of phosphatidylinositol 3'-kinase (PI 3-kinase) with IRS proteins was normal in cells treated with nelfinavir, as was IRS-1-associated PI 3-kinase activity. Yet insulin-induced phosphorylation of Akt/protein kinase B (PKB), p70S6 kinase and extracellular signal-regulated kinase 1/2 was significantly impaired. This could not be attributed to increased protein phosphatase 2A activity or to increased expression of phosphoinositide phosphatases (SHIP2 or PTEN). However, insulin failed to induce translocation of the PI 3-kinase effectors Akt/PKB and protein kinase C-zeta (PKC-zeta) to plasma membrane fractions of nelfinavir-treated adipocytes.

CONCLUSIONS/INTERPRETATION

We therefore conclude that nelfinavir induces a defect in the insulin signalling cascade downstream of the activation of PI 3-kinase. This defect manifests itself by impaired insulin-mediated recruitment of Akt/PKB and PKC-zeta to the plasma membrane.

Cbl PYXXM motifs activate the P85 subunit of phosphatidylinositol 3-kinase, Crk, atypical protein kinase C, and glucose transport during thiazolidinedione action in 3T3/L1 and human adipocytes

The thiazolidinedione (TZD), rosiglitazone, has previously been found to tyrosine-phosphorylate Cbl and activate Cbl-dependent phosphatidylinositol (PI) 3-kinase and atypical protein kinase Cs (aPKCs) while stimulating glucose transport in 3T3/L1 adipocytes. Presently, the role of Cbl in rosiglitazone action was further assessed in both 3T3/L1 and human adipocytes by expressing Y371F and/or Y731F mutant forms of Cbl that nullified the functionality of canonical pYXXM motifs in Cbl. These mutants diminished the interaction of Cbl with the p85 subunit of PI 3-kinase and inhibited subsequent increases in Cbl-dependent PI 3-kinase activity, aPKC activity, and glucose transport. These mutants also inhibited the interaction of Cbl with Crk, which has been implicated in the activation of other PI 3-kinase-independent signaling factors that have been found to be required during activation of glucose transport by insulin and other agonists. We conclude that pYXXM motifs in Cbl serve to activate PI 3-kinase-dependent and possibly PI 3-kinase-independent pathways that are required for TZD-dependent glucose transport in adipocytes.

Effects of peripheral administration of 5-hydroxytryptamine (5-HT ) on 2-deoxy-D-glucose-induced hyperphagia in rats

Effects of peripheral administration of 5-HT (5-hydroxytryptamine, serotonin) on hyperphagia induced by 2-deoxy-D-glucose(2-DG) were studied in rats. It was found that 5-HT i.p. reduced 2-DG-elicited feeding in rats dose-dependently. The 5-HT-induced hypophagia was antagonized by the 5-HT2A receptor antagonist, ketanserin. It is known that 2-DG induces glucoprivation, resulting in hyperphagia and hyperglycemia. However, 5-HT did not affect hyperglycemia induced by 2-DG. These results suggest that peripheral injection of 5-HT reduces 2-DG-induced hyperphagia mediated by the peripheral 5-HT2A receptor and that its effects are not due to enhancement of hyperglycemia.

Need for GLUT4 activation to reach maximum effect of insulin-mediated glucose uptake in brown adipocytes isolated from GLUT4myc-expressing mice

There is a need to understand whether the amount of GLUT4 at the cell surface determines the extent of glucose uptake in response to insulin. Thus, we created a heterozygous mouse expressing modest levels of myc-tagged GLUT4 (GLUT4myc) in insulin-sensitive tissues under the control of the human GLUT4 promoter. Insulin stimulated 2-deoxyglucose uptake 6.5-fold in isolated brown adipocytes. GLUT1 did not contribute to the insulin response. The stimulation by insulin was completely blocked by wortmannin and partly (55 +/- 2%) by the p38 mitogen-activated protein kinase (MAPK) inhibitor SB203580. Insulin increased surface exposure of GLUT4myc twofold (determined by fluorescent or enzyme-linked myc immunodetection in intact adipocytes). Such increase was completely blocked by wortmannin but insensitive to SB203580. Insulin increased the kinase activity of the p38 MAPK beta-isoform 1.9-fold without affecting p38-alpha. In summary, the GLUT4myc mouse is a promising model for measuring GLUT4 translocation in intact primary cells. It affords direct comparison between GLUT4 translocation and glucose uptake in similar cell preparations, allowing one to study the regulation of GLUT4 activity. Using this animal model, we found that stimulation of glucose uptake into brown adipocytes involves both GLUT4 translocation and activation.

The antihyperglycemic drug alpha-lipoic acid stimulates glucose uptake via both GLUT4 translocation and GLUT4 activation: potential role of p38 mitogen-activated protein kinase in GLUT4 activation

The cofactor of mitochondrial dehydrogenase complexes and potent antioxidant alpha-lipoic acid has been shown to lower blood glucose in diabetic animals. alpha-Lipoic acid enhances glucose uptake and GLUT1 and GLUT4 translocation in 3T3-L1 adipocytes and L6 myotubes, mimicking insulin action. In both cell types, insulin-stimulated glucose uptake is reduced by inhibitors of p38 mitogen-activated protein kinase (MAPK). Here we explore the effect of alpha-lipoic acid on p38 MAPK, phosphatidylinositol (PI) 3-kinase, and Akt1 in L6 myotubes. alpha-Lipoic acid (2.5 mmol/l) increased PI 3-kinase activity (31-fold) and Akt1 (4.9-fold). Both activities were inhibited by 100 nmol/l wortmannin. alpha-Lipoic acid also stimulated p38 MAPK phosphorylation by twofold within 10 min. The phosphorylation persisted for at least 30 min. Like insulin, alpha-lipoic acid increased the kinase activity of the alpha (2.8-fold) and beta (2.1-fold) isoforms of p38 MAPK, measured by an in vitro kinase assay. Treating cells with 10 micromol/l of the p38 MAPK inhibitors SB202190 or SB203580 reduced the alpha-lipoic acid-induced stimulation of glucose uptake by 66 and 55%, respectively. In contrast, SB202474, a structural analog that does not inhibit p38 MAPK, was without effect on glucose uptake. In contrast to 2-deoxyglucose uptake, translocation of GLUT4myc to the cell surface by either alpha-lipoic acid or insulin was unaffected by 20 micromol/l of SB202190 or SB203580. The results suggest that inhibition of 2-deoxyglucose uptake in response to alpha-lipoic acid by inhibitors of p38 MAPK is independent of an effect on GLUT4 translocation. Instead, it is likely that regulation of transporter activity is sensitive to these inhibitors.

Stimulatory effect of isoferulic acid on alpha1A-adrenoceptor to increase glucose uptake into cultured myoblast C2C12 cell of mice

In an attempt to elucidate the effect of isoferulic acid on alpha1-adrenoceptor (AR), the myoblast C2C12 cells of mice were employed to investigate the change of glucose uptake in the present study. Isoferulic acid enhanced the uptake of radioactive glucose into C2C12 cells in a concentration-dependent manner, which were abolished by pretreatment with prazosin. Effect of isoferulic acid on alpha1-AR was further characterized using the displacement of [3H]YM617 binding in C2C12 cells. The radioactive glucose uptake increasing action of isoferulic acid was abolished by tamsulosin or WB 4101 at concentration sufficient to block alpha1A-adrenoceptor (alpha1A-AR) but it was not modified by chlorethylclonidine (CEC) at the concentration sufficient to abolish alpha1B-AR. An activation of alpha1A-AR by isoferulic acid in C2C12 cells can thus be considered. Pharmacological inhibition of phospholipase C (PLC) by U73312 resulted in a concentration-dependent reduction of isoferulic acid-stimulated glucose uptake in C2C12 cells. This inhibition by U73112 was specific because the inactive congener, U73343, failed to modify the action of isoferulic acid. Also, chelerythrine and GF 109203X diminished the action of isoferulic acid at concentration sufficient to inhibit the activity of protein kinase C (PKC). The obtained data suggest that an activation of alpha1A-AR by isoferulic acid may increase the glucose uptake via PLC-PKC pathway in C2C12 cells.

Can experimental conditions explain the discrepancy over glutamate stimulation of aerobic glycolysis?

Uncertainty reigns over whether or not glutamate uptake in astrocytes leads to strong stimulation of glucose utilization, measured as accumulation of radioactive deoxyglucose-6-phosphate. This is an important issue, not only because glutamate is the major excitatory transmitter, but also because it has been postulated that glutamate-induced stimulation of glycolysis links brain excitation with activation of energy production. The effect of glutamate on deoxyglucose utilization in cultured rat and mouse astrocytes grown in different media and incubated under various conditions during the deoxyglucose assay has, therefore, been studied. Under most conditions, no stimulation occurred but rather a decrease in deoxyglucose utilization during exposure to glutamate; under certain conditions, the contribution of non-metabolized deoxyglucose to the intracellular 14C signal was significant.

Inhibition of glucose uptake and suppression of glucose transporter 1 mRNA expression in L929 cells by tumour necrosis factor-alpha

Recombinant human tumour necrosis factor-alpha (rhTNF-alpha) arrested the growth and suppressed glucose uptake of mouse fibrosarcoma L929 cells in vitro. When the cells were treated with rhTNF-alpha for 24 hours, the mRNA level of glucose transporter 1 (GLUT 1), which is the only GLUT found to be present in L929 cells in our study, was suppressed in a dose-dependent manner. Since the growth of tumour cells depends mainly on glucose catabolism, our findings may indicate that rhTNF-alpha inhibits L929 cells growth by lowering the glucose transport through suppression of GLUT 1 mRNA expression in the cells.

Ethanol inhibits G-protein-mediated glucose uptake by C6 glioma cells

The mechanism of ethanol inhibition of glucose uptake was investigated using C6 glioma cells. Basal [3H]2-deoxy-D-glucose (2DG) uptake by C6 cells was inhibited by ethanol in a concentration-dependent manner. Fifty, 75 and 100 mM ethanol significantly inhibited basal 2DG uptake by 12, 20 and 23%, respectively (p < 0.05). Carbachol (an agonist acting via G protein-coupled receptors) stimulated the uptake by 26% (p < 0.05). In the presence of 100 mM ethanol, the ability of carbachol to stimulate 2DG uptake was abolished. In contrast, ethanol did not inhibit the ability of insulin to stimulate 2DG uptake. These results suggest that ethanol inhibits 2DG uptake by selectively interfering with G protein-mediated signal transduction pathway.

QLS motif in transmembrane helix VII of the glucose transporter family interacts with the C-1 position of D-glucose and is involved in substrate selection at the exofacial binding site

The liver-type (GLUT2) and brain-type (GLUT3) human facilitative glucose transporters exhibit distinct kinetics (Km values for deoxyglucose transport of approximately 11 mM and approximately 1.5 mM, respectively) and patterns of substrate transport (GLUT2 is capable of D-fructose transport, while GLUT3 is not). Using a range of chimeric glucose transporters comprised of regions of GLUT2 and GLUT3 studied by expression in Xenopus oocytes after microinjection of cRNA, we have proposed that the seventh putative transmembrane helix is intimately involved in the selection of transported substrate and that this region plays an important role in determining the Km for 2-deoxyglucose [Arbuckle, M. I., Kane, S., Porter, L. M., Seatter, M. J., and Gould, G. W. (1996) Biochemistry 35, 16519-16527]. Inspection of the predicted amino acid sequence of this region reveals that GLUTs 1, 3, and 4 (high-affinity glucose transporters) contain a conserved QLS motif in this helix (residues 277-279 in human GLUT3). In the glucose/fructose transporter (GLUT2) this motif is replaced by HVA. To study the role of the QLS motif in substrate selection, we have engineered substitutions in this region between GLUT2 and GLUT3. GLUT3 (QLS > HVA) exhibits a Km for deoxyglucose transport identical to that of native GLUT3 but increased sensitivity for inhibition of deoxyglucose transport by D-fructose. However, unlike native GLUT3, this species is capable of transporting D-fructose. Compared to wild-type GLUT2, GLUT2 (HVA > QLS) exhibits a lower Km for deoxyglucose transport (approximately 3 mM vs approximately 11 mM), the ability to transport D-fructose is reduced, and D-fructose is a less efficient inhibitor of deoxyglucose transport. Analysis of the ability of a range of glucose epimers and analogues to inhibit transport by these species suggests that the QLS motif interacts with the incoming D-glucose at the C-1 position; this may be a key interaction in the high-affinity recognition of the transported substrate. We further argue that this interaction acts as a molecular filter that is involved in the selection of the transported substrate.

Inhibition of glucose transport in human red blood cells by adenosine antagonists

Previous studies have suggested that adenosine antagonists can interfere with normal glucose uptake in perfused rat heart. In the present studies, fluorine-19 nuclear magnetic resonance spectroscopy was used to study the effect of the adenosine antagonist, BW-A1433U, on the equilibrium exchange of fluorinated glucose analogs in human erythrocytes. Studies of the equilibrium exchange of both 2-fluoro-2-deoxy-D-glucose and 3-fluoro-3-deoxy-D-glucose with either one-dimensional magnetization transfer or two-dimensional exchange spectroscopy were performed, and significant inhibition was observed in all cases. From concentration-dependent studies, an inhibition constant for the equilibrium exchange measured at 37 degrees C of 24 microM was determined.

[Antiulcer properties of shosaiko-to]

Recently it has been reported that Shosaiko-to (SHO), a traditional Chinese medicine used for treating gastritis and hepatitis, also has been found useful for treating gastric ulcers, although no pharmacological study has yet investigated the precise antiulcer properties of SHO. Herein, the authors report on the results of a rat study in which the effects of SHO on gastric ulcers, acid secretions and potential difference of gastric mucosa (PD) were studied. SHO (100, 250 or 500 mg /kg, p.o.) significantly inhibited the development of ethanol-induced gastric lesions in a dose-dependent manner. SHO (500 mg/kg, p.o.) significantly inhibited the development of aspirin-,indomethacin- or water-immersion-stress induced gastric lesions. Sucralfate (500 mg/kg, p.o.) inhibited both ethanol- and aspirin-induced gastric lesions, and cimetidine (10 mg/kg, p.o.) inhibited aspirin-, indomethacin- or stress-induced gastric lesions. SHO (10, 30 and 100 mg/kg, i.p.) also significantly inhibited pentagastrin- and 2-deoxy-D-glucose (2-DG)-induced gastric acid secretions in a dose-dependent manner, whereas cimetidine (1 mg/kg, i.p.) inhibited a pentagastrin-induced secretion and atropine (0.05 mg/kg, i.p.) inhibited pentagastrin- or 2-DG-induced acid secretions. SHO (250, 500 or 1000 mg/kg, i.g.) significantly inhibited ethanol-induced PD reduction. Sucralfate (500 mg/kg, i.g.) inhibited the reduction, and cimetidine (250 mg/kg, i.g.) didn't inhibit it. These results indicate that SHO not only possesses the capability of protecting the rat gastric mucosa as well as sucralfate, but also is able to inhibit gastric acid secretions like cimetidine or atropine.

Salbutamol antagonizes insulin- and sodium mercaptoacetate-induced but not 2-deoxy-D-glucose-induced hyperphagia

The role of beta-adrenoreceptors in modulating feeding in glucoprivation- and lipoprivation-induced hyperphagias was studied in rats by measuring the efficacy of the selective beta2-adrenoreceptor agonist salbutamol to antagonize the hyperphagic response induced by injection of 2-deoxy-D-glucose (2-DG), insulin, or sodium mercaptoacetate (MA). 2-DG and insulin are blockers of glucose utilization, and their administration stimulates receptor cells that are selectively sensitive to central glucose availability. MA stimulates feeding in rats maintained on a fat-supplemented diet, by blocking fatty acid oxidation at different levels in the metabolic pathway. We found that salbutamol dose-dependently antagonized both the insulin- and MA-induced hyperphagia, with reductions in food intake up to 100% compared with rats treated with insulin or MA alone. On the contrary, salbutamol, even at the highest dose (15 mg/kg, IP), was completely ineffective against 2-DG-induced hyperphagia. The present results support the previously proposed notion that there are different neuronal or humoral circuits underlying the hyperphagic responses to the metabolic stimuli induced by glucoprivation (i.e., 2-DG and insulin administration), and they extend our knowledge on the effects of salbutamol on glucoprivic and lipoprivic control of feeding.

Interleukin-1 beta-mediated glucose uptake by chondrocytes. Inhibition by cortisol

The aim of this study was to investigate the in vitro effects of interleukin-1 beta (IL-1 beta) on cultured human articular chondrocytes from patients with osteoarthritis, by the evaluation of glucose uptake. We also investigated the inhibitory effect of cortisol on IL-1 beta-mediated glucose uptake. Experiments were performed by using 2-deoxy-D-[1-3H]glucose (2-DOG) and confluent monolayer cells at first passage. Confluent cells were also treated for 24 h with different concentrations of cortisol (10(-5), 10(-6) and 10(-7) mol/l). IL-1 beta (100 pg/ml) was added 6 h before glucose uptake studies. Glucose uptake stimulation was observed 3 h after the addition of 100 pg/ml IL-1 beta (+70%) and increased up to 24 h (+145%). The sensitivity and responsiveness of chondrocytes to IL-1 beta, studied after a 6 h association time, appeared to be dose-dependent from 0.1 pg/ml IL-1 beta (+50%) to 100 pg/ml (+130%) over basal values. The effect of the cytokine was protein synthesis-dependent, as demonstrated by using cycloheximide. Cortisol inhibited the action of IL-1 beta on glucose uptake because it reduced stimulating effects by 28% at concentrations as weak as 10(-6) mol/l. Results appeared similar when IL-1 beta and cortisol were added simultaneously 6 h before 2-DOG uptake. The rapid effect of cortisol was protein-synthesis dependent, as indicated by inhibition by cycloheximide. These results suggest that IL-1 beta stimulates chondrocyte metabolic activity. The inhibition of IL-1 beta-mediated glucose uptake is suggested for studying the anti-IL-1 effect of other anti-rheumatic drugs.

Intraventricular glucose blocks feeding induced by 2-deoxy-D-glucose but not mercaptoacetate

Previous results have shown that IV infusion of glucose reduces feeding induced by systemic administration of 2-deoxy-D-glucose (2-DG) or 2-mercaptoacetate (MA) in rats. Because glucose is a metabolic substrate for both central and peripheral tissues, the suppression of feeding by glucose could result from either a central or peripheral metabolic effect. In the present experiment we attempted to clarify the mechanism of glucose-induced suppression of feeding induced by 2-DG and MA by administering glucose centrally during systemic metabolic challenge. Administration of glucose into the lateral ventricle was begun immediately after systemic injection of 2-DG or MA and continued intermittently during the 2-h feeding test. We found that central glucose administration significantly reduced 2-DG- but not MA-induced feeding. These results suggest that the central effects of glucose are sufficient to suppress feeding induced by systemic 2-DG and support the hypothesis that receptors responsible for 2-DG-induced feeding are located in the brain.

Pharmacological and developmental evidence that the potassium-induced stimulation of deoxyglucose uptake in astrocytes is a metabolic manifestation of increased Na(+)-K(+)-ATPase activity

There is disagreement in the literature whether or not deoxyglucose accumulation, a measure of glycolytic activity, is increased in astrocytes during exposure to elevated concentrations of the potassium ion (K+). In the present work we have confirmed our previous finding that deoxyglucose accumulation in primary cultures of well-differentiated mouse astrocytes shows a robust increase when the K+ concentration in the incubation medium is raised to or above 12 mM. This response is inhibited by ouabain (with a half-maximum effect at approximately 0.1 mM), indicating that it is a metabolic manifestation of the activity of an Na(+)-K(+)-ATPase. The stimulation at this high level of K+ indicates a remarkably low K+ affinity of the Na(+)-K(+)-ATPase involved, enabling it to be activated by above-normal concentrations of K+. At a resting concentration of K+ (5.4 mM), at least one half of the deoxyglucose accumulation is also a reflection of Na(+)-K(+)-ATPase activity, as shown by its susceptibility to inhibition by ouabain. Ouabain has some effect even at a concentration of 0.1 microM, indicating participation of not only the alpha 1 isoform which has a low affinity to ouabain, but also of the alpha 2 isoform, which has a high affinity. The stimulatory effect of elevated K+ is absent in immature astrocytes and only develops after prolonged time in culture. It could not be evoked in a seemingly similar culture of rat astrocytes, which has previously been shown to lack Na(+)-K(+)-ATPase activity as well as the alpha 2 isoform of the ATPase. This isoform has unequivocally been found to be expressed by astrocytes in situ.

[Fructose 1,6-diphosphate can be a substrate to accelerate glycolysis]

Fructose 1,6-diphosphate (F1, 6P) is a glycolytic intermediate which has already been used clinically to treat congestive heart failure. F1, 6P has been shown experimentally to improve glycolytic flux, although theoretical background is unclear. Since there is two possible mechanism of F1, 6P effect on acceleration of glycolysis, including pharmacological effect and substrate effect, we sought to determine the real mechanism of action of F1, 6P on glycolysis. Langendorff-perfused rabbit hearts were infused with F1, 6P (5 and 10 mM) in a first group, and in a second group, 30 minutes of perfusion with modified Krebs-Henselit (K-H) buffer with reduced glucose concentration (5 mM), plus 2-deoxy glucose (5 mM) and with or without 10 mM F1, 6P followed by 30 minutes of wash with normal K-H buffer. We measured contractile function, oxygen consumption, and high energy phosphate by 31p-NMR spectroscopy. In the first group of experiments, F1, 6P resulted in a dose dependent increase in high energy phosphate production and inorganic phosphate (Pi). There was also a marked decline in developed pressure (Dev P) due mostly to the ability of F1, 6P to chelate calcium. Intracellular Mg2+ which was also reduced during F1, 6P infusion might be related to intracellular Ca2+ and/or accelerated glycolysis. In the model of glycolysis inhibited by 2-DG, Dev P was consistently decreased during the infusion of 2-DG, and wash-out period along with the deterioration of high energy phosphate. However, F1, 6P could provide excellent recovery of contractile function after wash along with superior high energy potential during the 2-DG infusion and wash.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute intragastric application of capsaicin inhibits 2-deoxy-D-glucose--but not histamine-induced gastric acid secretion in the dog

In this study the influence of acute exposure of gastric mucosa to the sensory neurotoxin capsaicin on basal gastric acid secretion and on secretion induced by 2-deoxy-D-glucose or histamine in conscious dogs with gastric fistulae has been investigated. Under basal conditions intragastric capsaicin (160 microM, 50 ml of volume) did not induce any significant change in acid secretion and in plasma levels of gastrin. Total acid output induced by 2-deoxy-D-glucose (75 mg/kg i.v.) was significantly decreased by intragastric application of capsaicin, while plasma gastrin concentrations were unaffected. A direct stimulant of the parietal cells, such as histamine (64 micrograms/kg s.c.) increased gastric acid secretion which was not sensitive to capsaicin pretreatment. These findings indicate the involvement of capsaicin-sensitive fibers in the control of vagally-induced gastric acid secretion in the dog.

Effect of prolactin on 2-deoxyglucose uptake in mouse mammary gland explants

These studies were carried out to explore the possible effect of prolactin (PRL) on glucose uptake into culture mammary gland explants derived from 12- to 14-day pregnant mice. PRL was found to stimulate an increased rate of uptake of a nonmetabolized glucose analogue, 2-[3H]deoxyglucose, into cultured mammary tissues. The onset of this response was 16 h after the addition of PRL, and the response persisted for at least 24 h. A similar temporal response was observed when the PRL stimulation of [14C]glucose oxidation to 14CO2 was determined. The lowest PRL concentration that elicited a stimulation of 2-deoxyglucose uptake was 20 ng/ml, and a maximum response occurred with PRL at a concentration of 250 ng/ml. Ongoing protein synthesis appears to be essential for PRL to express its effect on 2-deoxyglucose transport since cyclohexamide, puromycin, and actinomycin D abolished the PRL response. It is also apparent that the PRL stimulation of 2-deoxyglucose involves activation of a specific carrier-mediated uptake transport system, since the rate of uptake of L-glucose into mouse mammary gland explants was unaffected by PRL.

Effect of modafinil on pancreatic exocrine secretion in the rat. A comparison with methadone

Modafinil is a recently developed drug which increases wakefulness in several animal species and in man, an effect involving, at least in part, central adrenoceptors. In the present experiments, the effect of modafinil was studied on a model of neurally stimulated secretion, pancreatic secretion induced by 2-deoxyglucose (2DG) in the rat, and compared with that of the mu-opiate methadone. Modafinil induced a dose-related inhibition of 2DG-stimulated pancreatic secretion, reaching more than 80% after 250 mg/kg i.p. The modafinil effect was suppressed by idazoxan or by large doses of prazosin but not by naloxone. In addition modafinil (250 mg/kg i.p.) did not change the pancreatic response to electrical vagal stimulation. Methadone also potently suppressed 2DG-stimulated pancreatic secretion, but in contrast to modafinil, the methadone effect was blocked by naloxone, but not by the adrenoceptor antagonists idazoxan, prazosin and propranolol. It is concluded that modafinil decreases centrally 2DG-stimulated pancreatic secretion through a pathway involving alpha 1- and alpha 2-adrenoceptors, without an interaction with opiate receptors.

[Effects of NIK-228 on gastric acid secretion in rats using the congo red sprayed method]

We have reported the antiulcer activities of a new compound that we named NIK-228 (3-hydroxy-methyl-2-methylimidazo [2, 1-b] benzothiazole). In the present report, we studied the antisecretory effects of NIK-228 on basal and stimulated gastric acid secretion using the Congo red sprayed method. Male Wistar rats (200 to 250 g) were used after 24 hr of fasting (without water). NIK-228, atropine and cimetidine were administered orally or intravenously 1 hr before operation for Congo red spraying. NIK-228 (100 mg/kg, p.o.), atropine (5 mg/kg p.o.) and cimetidine (100 mg/kg, p.o.) all inhibited basal gastric acid secretion. Oral administration of NIK-228 and atropine inhibited gastrin, 2-deoxy-D-glucose (2-DG) and bethanechol-induced acid secretion, but didn't inhibit histamine-induced acid secretion. Cimetidine inhibited all of histamine, gastrin, 2-DG and bethanechol-induced acid secretion. In vagotomized rats, oral and intravenous administration of atropine both inhibited bethanechol-induced acid secretion, but NIK-228 was not inhibited. These results suggested that antisecretory effects of NIK-228 were caused by the central vagal systems.

Specificity and kinetics of hexose transport in Trypanosoma brucei

Transport of 6-deoxy-D-glucose was studied in Trypanosoma brucei in order to characterise the kinetics of hexose transport in this organism using a nonphosphorylated sugar. Kinetic parameters for efflux and entry, measured using zero-trans and equilibrium exchange protocols, indicate that the transporter is probably kinetically symmetrical. Comparison of the kinetic constants of D-glucose metabolism with those for 6-deoxy-D-glucose transport shows that transport across the plasma membrane is likely to be the rate-limiting step of glucose utilisation. The transport rate is nevertheless very fast and 6-deoxy-D-glucose, at concentrations below Km, enters the cells with a half filling time of less than 2 s at 20 degrees C. Thus the high metabolic capacity of these organisms is matched by a high transport rate. The structural requirements for the trypanosome hexose transporter were explored by measuring inhibition constants (Ki) for a range of D-glucose analogues including fluoro and deoxy sugars as well as epimeric hexoses. The relative affinities shown by these analogues indicated H-bonds from the carrier to the C-3, C-4 and C-5 hydroxyl oxygens and from the C-1 and C-3 hydroxyl hydrogens to the binding site. Hydrophobic interactions are likely at the C-2 and C-6 regions of the glucose molecule. Spatial constraints appear to occur around C-4 indicating that the transport site at this position is not freely open to the external solution as is the case with the mammalian hexose transporter. However, the trypanosome transporter appears to accept D-fructose but the common mammalian (erythrocyte type) hexose transporter does not.

Increase in gastric secretion induced by 2-deoxy-D-glucose is impaired in capsaicin pretreated rats

Gastric acid secretion was determined following intravenous administration of 2-deoxy-D-glucose (2-DG; 60 mg kg-1) or electrical stimulation of the vagus nerve in urethane-anaesthetized rats pretreated when newborn with either capsaicin or the vehicle. The secretory response to 2-DG was substantially reduced in the capsaicin pretreated rats, while that induced by electrical vagal stimulation (1 mA, 1 ms. 3 Hz) was unaffected. These results suggest that capsaicin-sensitive fibres are involved in the afferent branch of the reflex response activated by 2-DG to stimulate gastric acid secretion.

[Pharmacological studies of some traditional Chinese medicines on gastric functions. (2) The effects of oren-gedoku-to (OGT), san'o-syasin-to (SST), antyu-san (AS) and dai-saiko-to (DST) on gastric acid secretion in rats]

The effects of OGT, SST, AS and DST on gastric acid secretion stimulated by histamine, pentagastrin, carbachol and 2-deoxy-D-glucose (2-DG) were studied in the perfused stomach of anesthetized rats, and these effects were compared with those of cimetidine, 16,16-dimethyl-prostaglandin E2(DMPGE2) and atropine. OGT and SST showed little or no effect on the acid secretion induced by histamine or carbachol at doses of 100 mg/kg, whereas the former showed a moderate inhibition and the latter showed a marked one against pentagastrin-stimulation. AS and DST had no effect on the acid secretion induced by carbachol at doses of 100 mg/kg, whereas they showed a moderate inhibition against histamine-stimulation, and the latter showed a significant inhibition against pentagastrin-stimulation. Further, each of the above four drugs showed a significant effect on 2-DG-stimulation. Cimetidine (1-10 mg/kg) inhibited gastric acid secretion stimulated by histamine, pentagastrin, carbachol or 2-DG in a dose-dependent manner. Similarly, DMPGE2 (10 micrograms/kg) strongly inhibited acid secretion induced by the four secretagogues. Atropine (50 micrograms/kg) inhibited acid secretion induced by carbachol or 2-DG, but not that by histamine or pentagastrin. These results suggest that OGT, SST, AS and DST clearly affect the mechanism of gastric acid secretion, and the site of action of OGT may differ from those of SST, AS and DST.

Morphine inhibits the gastric acid secretion stimulated by 2-deoxy-D-glucose via a central mechanism in anesthetized rats

The effect of morphine on the gastric acid secretion induced by 2-deoxy-D-glucose (2-DG) was investigated in the perfused stomach of anesthetized rats. The intravenous infusion of morphine (0.01-1.0 mg/kg per h for 2 h) dose dependently suppressed the gastric acid secretion stimulated by 2-DG. This inhibitory effect of morphine was completely reversed by naloxone (1.0 mg/kg i.v.) pretreatment. On the other hand, even the higher dose of morphine (1.0 mg/kg per h for 70 min) had no effect on the gastric acid secretion evoked peripherally by electrical stimulation of the vagus nerve. These observations indicate that morphine suppressed the 2-DG-induced gastric acid secretion via a central mechanism(s), probably mediated by the opiate receptor(s).

Inhibition of 2-deoxy-glucose-induced glucagon secretion by muscarinic and alpha-adrenoceptor blockade in the mouse

Neuroglycopenia induced by 2-deoxy-glucose is known to activate the autonomic nervous system and to stimulate glucagon secretion. In this study, the relative contribution of the various branches of the autonomic nervous system on the 2-deoxy-glucose-induced glucagon secretion was investigated in the mouse. An intravenous injection of 2-deoxy-glucose (500 mg/kg) was followed by a 5-fold increase in plasma levels of glucagon (P less than 0.001). This 2-deoxy-glucose-induced glucagon secretion was impaired by pre-treatment with either the muscarinic antagonist methylatropine (by 83%; P less than 0.001) or the nicotinic antagonist hexamethonium (by 90%; P less than 0.001). Further, also the alpha-adrenoceptor antagonist phentolamine inhibited the glucagon response to 2-deoxy-glucose (by 35%; P less than 0.01). In contrast, the beta-adrenoceptor antagonist L-propranolol did not affect the glucagon response to 2-deoxy-glucose. It is concluded that the main mechanism behind the increased plasma levels of glucagon following administration of 2-deoxy-glucose is cholinergic activation. However, intact alpha-adrenoceptors are a pre-requisite for the full effect of 2-deoxy-glucose. In contrast, beta-adrenoceptors seem to be of no importance and there seems to be no room for neuropeptides as mediators of the neuroglycopenia-induced glucagon secretion in the mouse.

Effect of peptide YY on cephalic, gastric, and intestinal phases of gastric acid secretion and on the release of gastrointestinal hormones

The objective of this study was to investigate the effects of a novel gut peptide, peptide YY (PYY), on the cephalic, gastric, and intestinal phases of gastric acid secretion and to explore the mechanisms involved. The cephalic phase of gastric acid secretion, stimulated by the intravenous injection of 2-deoxyglucose (75 mg/kg), was found to be inhibited by intravenous PYY (100, 200, 400 pmol/kg X h) in a dose-related fashion. Peptide YY (200 and 400 pmol/kg X h) also resulted in a significant dose-dependent inhibition of the gastric phase of acid secretion. On the other hand, PYY (400 pmol/kg X h) failed to affect the intestinal phase of gastric acid output. Serum gastrin levels were increased on infusion of 10% liver extract into stomach, but were unaffected on instillation of liver extract into duodenum. Peptide YY did not inhibit the release of gastrin in either the gastric or intestinal phase studies. Furthermore, PYY had no significant effect on either the basal release of secretin, gastric inhibitory polypeptide, pancreatic polypeptide, or neurotensin, or on the stimulated release of pancreatic polypeptide by 2-deoxyglucose. The specific binding of gastrin to its receptors on the fundic mucosa was also unaffected by PYY. These results indicate that PYY inhibits the cephalic and gastric phases of acid secretion independently, and that its actions are not mediated by either a negative effect on gastrin release or a positive effect on the release of some of the known acid inhibitors, or by an inhibition of gastrin binding to its receptors on the fundic cells. Our present findings (in combination with our previous findings of inhibition of pentagastrin- and bethanechol-stimulated gastric acid secretion by PYY, independent of the vagal cholinergic mechanism) indicate that the action of PYY is either direct on the parietal cells or is mediated by yet another, unidentified, inhibitor.

Reduction in 2-deoxy-D-glucose analgesia following acute, but not chronic antidepressant treatment

Acute, but not chronic, antidepressant treatment potentiates the analgesic responses following cold-water swims. The present study evaluated the effects of acute (10 mg/kg) and chronic (10 mg/kg, twice daily over 7 days) pretreatment with desipramine (DMI) upon the analgesic response following 2-deoxy-D-glucose (2DG) in rats as measured by the jump test. Acute, but not chronic, DMI pretreatment significantly reduced 2DG analgesia. These effects are discussed in terms of the heterogeneity of pain-inhibitory responses.

Reduction of centrally-stimulated gastric acid secretion by tizanidine, a new imidazoline derivative, in anesthetized rats

The effect of a novel imidazoline derivative (tizanidine) on stimulated gastric acid secretion was studied in the perfused stomach of anesthetized rats. Tizanidine, which did not prevent peripherally-stimulated gastric acid secretion, inhibited 2DG- or TRH-stimulated gastric acid secretion. Yohimbine and phentolamine reduced the inhibition of TRH-stimulated acid secretion by tizanidine. Clonidine was found to have similar effects to tizanidine at a lower dose. These results indicate that tizanidine may inhibit gastric acid secretion via the central alpha-adrenergic system similar to clonidine in anesthetized rats.

Guanethidine blocks the 2-deoxy-D-glucose-induced hypothalamic noradrenergic drive to hyperglycemia

To determine whether 2-deoxy-D-glucose (2-DG)-induced hyperglycemia is neurally mediated we administered guanethidine, an adrenergic neuron blocker, to 2-DG-treated rats. While 2-DG increased both medial basal hypothalamic noradrenergic neuronal activity (MBH NNA) and serum glucose, the rise in serum glucose was blocked by guanethidine while MBH NNA was even further increased. We conclude that 2-DG-induced hypothalamic noradrenergic drive to hyperglycemia is mediated by direct sympathetic nervous system activation of liver glucose output.

Naloxone inhibits the plasma epinephrine response to ACTH but not to 2-deoxy-D-glucose in rats

Intravenous injection of (1-24) ACTH and 2-deoxy-d-glucose (2DG) stimulated the plasma epinephrine and norepinephrine levels in pentobarbital-anesthetized male rats. Naloxone, a specific opiate antagonist, inhibited the plasma epinephrine response to ACTH but not to 2DG. Norepinephrine release induced by ACTH or 2DG was not affected by naloxone. These results suggest that the opioid peptidergic synapse might be involved in the ACTH- but not in the 2DG-induced epinephrine release.

Estradiol and progesterone suppress feeding induced by 2-deoxy-d-glucose☆

The feeding response to 2-deoxy-d-glucose (2DG) was measured in gonadally intact females (NORM) during estrus (EST) or diestrus (DIES) and in ovariectomized (OVEX) rats following injections of estradiol benzoate and progesterone (HORM) or oil (OIL). In both groups the response to 2DG under conditions of EST or HORM was significantly suppressed relative to DIES or OIL. The suppressant effect of hormones on 2DG feeding was not accounted for by the suppressant effects of ovarian hormones on ad lib feeding or a function of the body weight of the subject. The results are discussed in the context of ovarian hormonal effects on glucostatic control of feeding.

[Mazindol effects on the salivary and gastric acid secretory mechanisms]

The effects of mazindol on the salivary secretion of dogs was investigated. Mazindol (2 mg/kg, i.v.) decreased the volume and pressure of salivary secretion induced by either chemical (carpronium) stimulation or electrical nerve stimulation. It also reduced spontaneous salivary secretion. Secretion velocity in the mazindol treated group was significantly less than in the physiological saline administered control group at 4 to 6 min after injection. Saline and mazindol produced no significance differences in Na+, Cl- or K+ concentrations in the saliva or serum. Thus mazindol inhibition of salivary secretion was not caused by ion transport. The existence of some other inhibitory mechanism is suggested. The effects of mazindol on the peripheral and central control of gastric acid secretion was also investigated in rats. Gastric acid secretion induced by direct application of cholinergic agents on oxyntic cells was not affected by mazindol. Gastric acid secretion induced by insulin and/or 2-DG, on the other hand, was markedly inhibited by intra-hypothalamic injection or systemic (i.v.) injections of mazindol. Electro-osmotic mazindol mimicked the effects of glucose in the lateral (inhibition) and ventromedial (excitation) hypothalamus. The results suggest that the inhibitory effects of mazindol on salivary secretion may be through the hypothalamic feeding control centers. Mazindol also directly affected gastric acid secretory neurons in the lateral hypothalamus. It might thus be expected to be effective in the treatment of obesity.

Bromocriptine inhibits 2-deoxy-D-glucose-stimulated gastric acid secretion in the rat

The influence of bromocriptine on the secretagogue-induced gastric acid secretion was examined in rats. The drug inhibited the gastric acid secretion centrally stimulated by 2-deoxy-D-glucose (2DG) in anesthetized or conscious rats. Apomorphine also prevented 2DG-induced acid secretion in anesthetized rats but not in conscious rats. Neither bromocriptine nor apomorphine significantly influenced the acid secretion induced peripherally by electrical vagus stimulation or gastrin. The antisecretory effect of bromocriptine was reversed by dopamine antagonists in anesthetized or conscious rats, but not by apomorphine in anesthetized rats. The results suggest that in rats, the antisecretory effect of bromocriptine on 2DG-stimulated acid secretion is partly due to its central dopamine agonistic action, but that of apomorphine may be due to dopaminergic plus other mechanisms.

Glucoprivic feeding is impaired by lateral or fourth ventricular alloxan injection

Feeding and blood glucose responses to insulin and 2-deoxy-D-glucose (2-DG) were examined in rats previously given lateral or fourth ventricular injections of the diabetogenic agents, alloxan and streptozotocin. Although streptozotocin (120, 200, and 400 micrograms) was ineffective, lateral ventricular alloxan injections (40 micrograms in 5 microliters) reduced feeding to 45% of control after 350 mg/kg 2-DG (sc), 33% of control after 150 mg/kg 2-DG, and 65% of control after insulin (2 U/kg). Fourth ventricular alloxan injections produced greater deficits, reducing feeding to 19, 7, and 46% of control, respectively. The sympathoadrenal response to glucoprivic agents was normal after alloxan treatment; however, blood glucose levels fell more rapidly during fasting than in controls. Alloxan-induced deficits did not appear to result from damage to catecholamine neurons, since neither regional concentrations nor glucoprivation-induced elevation of catecholamine turnover was altered by alloxan pretreatment. We conclude that cells involved in the glucoprivic control of feeding can be selectively and permanently damaged by intracerebroventricular alloxan administration. Such cells appear to reside in the hindbrain, to be noncatecholaminergic, and to function independently of glucoreceptors mediating sympathodrenal discharge.

Reversal of 2-deoxyglucose inhibition of serotonin uptake in isolated guinea pig lung

The effect of various substrates on the rate of uptake of 5-hydroxytryptamine (serotonin) from the pulmonary circulation was studied with isolated guinea pig lungs. Lungs were ventilated and were perfused with an electrolyte solution in a recirculating system. Uptake of serotonin was calculated from the rate of disappearance of [14C]serotonin from the perfusate. Serotonin uptake was inhibited by approximately 40% when 5 mM 2-deoxyglucose was substituted for glucose in the pulmonary perfusate. The inhibition due to 2-deoxyglucose was reversed by addition to the perfusate of pyruvate, lactate, acetate, alanine, beta-hydroxybutyrate, palmitate, or glycerol. Fructose ans succinate were less efficient substrates while no significant effect was noted with L-glycerol 1-phosphate or L-phenylalanine. These results indicate that a wide variety of metabolizable substrates can be utilized by the pulmonary endothelium to support uptake of serotonin.

Intraventricular alloxan eliminates feeding elicited by 2-deoxyglucose

Evidence suggests that alloxan reacts with membrane-bound glucoreceptors and that it competes with glucose molecules for these sites. We therefore administered small quantities of alloxan into the cerebrospinal fluid of rats to determine what effect this might have on their ability to react to changes of glucose concentration. Rats treated in this manner did not eat as much as controls in response to the intraperitoneal administration of 2-deoxyglucose or to a 24-hour fast, and they became hypoglycemic significantly sooner than controls when fasted. The data suggest that the function of brain glucoreceptors is to protect the body from sudden decreases of glucose and that these glucoreceptors play little if any role in the normal regulation or maintenance of feeding, body weight, or blood glucose concentrations.

[Effects of gamma-oryzanol and atropine on gastric secretion stimulated by insulin or 2-deoxy-D-glucose (author's transl)]

The inhibitory effects of gamma-oryzanol and atropine on the gastric secretion were studied using insulin and 2-deoxy-D-glucose as vagal stimulants. Pretreatment with gamma-oryzanol (100 mg/kg, s.c., once daily x 5) depressed the gastric secretion stimulated by insulin or 2-deoxy-D-glucose, but the potency was less than that with atropine (10 mg/kg, s.c.). gamma-Oryzanol had no effect on decrease in the serum glucose level or on increase in the gastrin level induced by insulin injection, while atropine enhanced these responses. From these results, it is considered that the inhibitory action of gamma-oryzanol on gastric secretion may be due to depression of the vagus system but the mode of action is different from that of atropine.

Methadone blockade of 2-deoxyglucose-induced pancreatic secretion in the rat

The effects of methadone on pancreatic exocrine secretions in the rat were tested under basal conditions and after hormonal stimulation by secretin and caerulein or after stimulation of the differentially acting cholinergic agents acetylcholine, 2-deoxyglucose, and electrical stimulation of the vagus. Methadone had no effect on basal hydroelectrolytic secretion. It decreased basal enzyme secretion very slightly under our experimental conditions. The stimulatory effects of 75 mg of 2-deoxyglucose per kg were completely blocked by methadone at 5 mg per kg and this blockade was reversed by nalorphine at 6 to 9 mg per kg. It was found that there are doses of methadone (100 microgram) which block 2-deoxyglucose effects when injected into brain ventricles but are ineffective when systemically introduced. The effects of secretin, caerulein, acetylcholine, and electrical stimulation of the vagus were not depressed by methadone. These results strongly suggest that the methadone blockade of 2-deoxyglucose effects occurs at a central level and is mediated by narcotic drug receptors.