Glucose transport in developing Ehrlich ascites tumor cells: parallel changes in the rate of glucose uptake and cytochalasin B binding activity during tumor development and methotrexate treatment

Effects of 4-alkylmorpholine N-oxides on ATP-producing processes in Ehrlich ascites and L1210 leukaemia cells

The main purpose of the present investigation was to study the effect of the homologous series of 4-alkylmorpholine N-oxides on ATP-producing processes in Ehrlich ascites and L1210 murine leukaemia cells. The effects on aerobic glucose consumption, lactic acid formation, content of total (T-SH) and non-protein thiol groups (NP-SH), endogenous and exogenous respiration and the level of ATP in tumour cells incubated in vitro were investigated. 4-Dodecylmorpholine N-oxide (DMNO), one of the most active compounds, decreased the level of ATP immediately after addition to the suspension of Ehrlich cells in an ice bath. After 2 h incubation at 37 degrees C the drop in the ATP level was much lower. A possible explanation for the decrease in the ATP level might be interaction of the amine oxide with the cell membrane.

A new insulin-mimetic vanadyl complex, (N-pyridylmethylaspartate)oxovanadium(IV) with VO(N2O2) coordination mode, and evaluation of its effect on uptake of D-glucose by Ehrlich ascites tumour cells

Because it has been confirmed that the vanadyl(IV) ion and its complexes act as insulin mimetics, a new organic vanadyl complex, (N-pyridylmethylaspartate)oxovanadium (VOPASP) with VO(N2O2) coordination mode, was prepared. Development of a simple and rapid in-vitro assay is needed for recognition of potent insulin-mimetic complexes. Treatment of Ehrlich ascites tumour cells with 2-deoxyglucose in the presence of vanadyl sulphate, or other vanadyl complexes with the same coordination mode (VOPASP, bis(picolinate)oxovanadium (VOPA) and bis(6-methyl picolinate)oxovanadium (VOMPA)), in the presence of 2-deoxy-D-[1-3H]glucose ([3H]deoxyglucose), resulted in concentration-dependent uptake of 2-deoxyglucose by the cells. The responses of the cells to the vanadyl complexes were reflected, in part, by results obtained from the free fatty acid-releasing assay using rat adipocytes. These results show that the in-vitro assay with Ehrlich ascites tumour cells provides an accurate and rapid assessment of glucose uptake by the cells. The assay is proposed as a means of predicting the insulin-mimetic activity of the vanadyl complexes and for studying the mechanism of action of the complexes.

Increases in mRNA levels of glucose transporters types 1 and 3 in Ehrlich ascites tumor cells during tumor development

A common feature of many tumors is an increase in glucose catabolism during tumor growth. We studied the mechanism of this phenomenon by using Ehrlich ascites tumor bearing mice as the animal model. We found that Ehrlich ascites tumor cells possess only glucose transporter 1 (GLUT1) and GLUT3 but not GLUT2, GLUT4, or GLUT5. The mRNA levels of GLUT1 and GLUT3 increased progressively in the tumour during development; however, there were no changes observable in mRNA levels of glucose transporters of all types in brain, liver, and heart of the host mice. These findings suggest that Ehrlich ascites tumor augments its glucose transport mechanism relative to other tissues in response to its unique growth needs.

Human tumour necrosis factor-alpha inhibits glucose transport in cultured Ehrlich ascites tumour cells

Human recombinant tumour necrosis factor-alpha (rhTNF-alpha) arrested the growth of Ehrlich ascites tumour (EAT) cells in vitro. It suppressed cellular glucose uptake and decreased the membrane density of glucose transporters as measured by glucose-reversible cytochalasin B binding. The glucose transporters' affinity for substrate was also reduced. However, rhTNF-alpha treatment exerted no effect on the phosphoribosyl pyrophosphate level in EAT cells. The role of rhTNF-alpha on the inhibition of glucose transport of tumour cells is discussed.

Metabolic and transcriptional changes in osteosarcoma cells treated with chemotherapeutic drugs

Two cell lines derived from a lung metastasis of a rat osteosarcoma were treated with cisplatin (CDDP) and two phosphonic acid compounds (AMDP, DADP), AMDP-treated cells showed a decrease in FDG uptake, CDDP and DADP resulted in an increase. A block in G2 or in S and G2 phase was seen after CDDP and AMDP treatment. The changes in the cell cycle fractions were not related to the changes in FDG uptake. Furthermore, the transcription of the glucose transporter and hexokinase genes were elevated in CDDP and decreased in AMDP treated cells. However, the changes in FDG uptake were not fully explained by changes at the transcriptional level. The total uptake of thymidine was elevated although the incorporation of thymidine into DNA decreased. In both cell lines the changes in FDG uptake correlated with the changes in thymidine incorporation into DNA (r = 0.95 and r = 0.83, respectively). Cells with an increased FDG uptake showed a weaker growth inhibition than cells with a decrease in FDG uptake.

Cloturin: effect on energy-producing processes in Ehrlich ascites and P388 murine leukaemia cells

The main purpose of the present investigation was to study the effect of cloturin on aerobic glycolysis, endogenous and exogenous respiration and the level of ATP in both Ehrlich ascites carcinoma (EAC) and P388 murine leukaemia cells incubated in vitro. Also its effect on the level of total (T-SH) and non-protein (NP-SH) thiol groups was investigated. A significant inhibition of aerobic glycolysis was found only in P388 cells after 60 min of cloturin action. Cloturin inhibited both endogenous and exogenous respiration of EAC with succinate as substrate. Cloturin decreased the level of ATP after 2 h incubation in both types of tumour cell. The level of NP-SH was decreased more than that of T-SH in both types of cell.

Intracellular phosphoribosyl diphosphate level and glucose carrier in Ehrlich ascites tumour cells during tumour growth and diabetes in tumour-bearing mice

The ability of Ehrlich ascites tumour (EAT) cells in mice to take up glucose as well as the density of glucose carriers on the cells increased progressively during the course of tumour development. Simultaneously as the rate of uptake rose, the intracellular phosphoribosyl diphosphate (PRPP) levels dropped responding to the decrease of serum glucose. Hyperglycaemia induced in the host by alloxan or streptozotocin administration increased the serum glucose concentrations and intracellular PRPP levels but decreased the density of glucose carriers of the cells, whereas insulin administration reversed this condition. The physiological significance of these observations are discussed.

Prevention by thymidine against toxicity and glucose uptake inhibition of methotrexate on cultured Ehrlich ascites tumour cells

Methotrexate (MTX) arrested cell growth and inhibited 2-deoxy-D-glucose uptake of Ehrlich ascites tumour cells in vitro. The changes of glucose concentrations in the culture media did not affect the degree of suppression of cell growth by MTX. Thymidine (dThd) protected against the toxic effect of MTX on the cells. It also prevented the inhibition effect on glucose uptake of the cells by MTX. MTX significantly suppressed the maximal uptake rate of glucose (Vmax) while addition of dThd alleviated the suppression. The half-saturation constant of the uptake (Km) remained constant.

Asymmetric reconstitution of the glucose transporter from Ehrlich ascites cell plasma membrane: role of alkali cations

Gel chromatography of solubilized Ehrlich cell plasma membranes and preformed asolectin vesicles coupled to a freeze-thaw cycle results in the reconstitution of 3-O-methyl-D-glucose transport. The transport activity of the liposomes formed is critically dependent on the cation present during reconstitution. Liposomes formed in K+ show high levels of carrier-mediated 3-O-methyl-D-glucose uptake (495 pmol/min/mg protein) while those formed in Na+ do not (33 pmol/min/mg protein). The inactivity in Na+ is not due to a diminished incorporation of glucose transporter nor is it due to carrier molecules reconstituted with a different orientation from those in K+ liposomes. Instead, the low glucose transport level in Na+ liposomes is related to the small size of vesicles formed with Na+. A second freeze-thaw cycle in K+ causes a two- to threefold increase in the available intravesicular volume of Na+ liposomes and results in an eightfold increase in carrier-mediated 3-O-methyl-D-glucose uptake. K+ liposomes, treated in an identical manner, show only a twofold increase in uptake. The glucose transporter was identified as a protein with a molecular mass range of 44.7 to 66.8 kDa, by the D-glucose-inhibitable photoincorporation of [3H]cytochalasin B. The carrier protein is inserted in reconstituted vesicles in a nonrandom manner with at least 80% of the molecules oriented with the cytoplasmic domain accessible to the external medium. In contrast, the neutral Na+-dependent amino acid transport system appears to be randomly reconstituted.

Glucose regulates its own transport in Ehrlich ascites tumour cells

The capacity of Ehrlich ascites tumour cells to take up 2-deoxy-D-glucose and to bind cytochalasin B varies adaptatively with the level of glucose in the plasma or culture medium. The effect of glucose is exerted directly on the cells and does not necessarily require the participation of hormones such as insulin, glucagon or corticosterone, although glucagon and the glucocorticoids, but not insulin, can also increase the number of glucose carrier molecules administered in vitro. Cycloheximide suppresses the acute inductive effect of glucose, suggesting that protein synthesis might be required for the increased transport activity.

Inhibition by N-(phosphonacetyl)-L-aspartate of Ehrlich ascites tumour growth and glucose transport

N-(Phosphonacetyl)-L-aspartate (PALA) suppressed the growth of Ehrlich ascites tumour cells in vivo in a dose-dependent manner. Simultaneously as the growth rate decreased, the cellular uptake of glucose and the density of a class of glucose-reversible binding sites for cytochalasin B on the cell surface were also found to be reduced. There is a highly significant correlation between the magnitude of changes in the number of cytochalasin B binding sites and the magnitude of changes in glucose uptake. The physiological significance of these observations are discussed.