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Apical and basolateral localisation of GLUT2 transporters in human lung epithelial cells.

Kalsi KK, Baker EH, Medina RA, Rice S, Wood DM, Ratoff JC, Philips BJ, Baines DL - Pflugers Arch. (2008)

Bottom Line: In non-polarised H441 cells, uptake of D: -glucose and deoxyglucose was similar.We could not conclusively demonstrate sodium/glucose transporter-mediated transport in non-polarised or polarised cells.We speculate that these transporters could contribute to glucose uptake/homeostasis in the human airway.

View Article: PubMed Central - PubMed

Affiliation: Centre for Ion Channel and Cell Signalling, Division of Basic Medical Sciences, St George's, University of London, Cranmer Terrace, London, SW17 0RE, UK.

ABSTRACT
Glucose concentrations of normal human airway surface liquid are approximately 12.5 times lower than blood glucose concentrations indicating that glucose uptake by epithelial cells may play a role in maintaining lung glucose homeostasis. We have therefore investigated potential glucose uptake mechanisms in non-polarised and polarised H441 human airway epithelial cells and bronchial biopsies. We detected mRNA and protein for glucose transporter type 2 (GLUT2) and glucose transporter type 4 (GLUT4) in non-polarised cells but GLUT4 was not detected in the plasma membrane. In polarised cells, GLUT2 protein was detected in both apical and basolateral membranes. Furthermore, GLUT2 protein was localised to epithelial cells of human bronchial mucosa biopsies. In non-polarised H441 cells, uptake of D: -glucose and deoxyglucose was similar. Uptake of both was inhibited by phloretin indicating that glucose uptake was via GLUT-mediated transport. Phloretin-sensitive transport remained the predominant route for glucose uptake across apical and basolateral membranes of polarised cells and was maximal at 5-10 mM glucose. We could not conclusively demonstrate sodium/glucose transporter-mediated transport in non-polarised or polarised cells. Our study provides the first evidence that glucose transport in human airway epithelial cells in vitro and in vivo utilises GLUT2 transporters. We speculate that these transporters could contribute to glucose uptake/homeostasis in the human airway.

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Uptake of glucose (traced by [3H]-glucose) by non-polarised H441 cells incubated in culture medium containing 1 mM (a), 5 mM (b) or 15 mM (c) glucose. Cells were pre-incubated with vehicle (control), 500 μM phlorizin (PZ) or 1 mM phloretin (PT) before measurement of glucose uptake. Uptake experiments were performed at 37°C. Data are presented as mean ± SEM. **p < 0.01, significantly different from control
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Fig2: Uptake of glucose (traced by [3H]-glucose) by non-polarised H441 cells incubated in culture medium containing 1 mM (a), 5 mM (b) or 15 mM (c) glucose. Cells were pre-incubated with vehicle (control), 500 μM phlorizin (PZ) or 1 mM phloretin (PT) before measurement of glucose uptake. Uptake experiments were performed at 37°C. Data are presented as mean ± SEM. **p < 0.01, significantly different from control

Mentions: Glucose uptake by non-polarised cells was measured following incubation in culture medium containing a range of physiological glucose concentrations: 1 mM (hypoglycaemic); 5 mM (normoglycaemic); 10 mM (mildly hyperglycaemic) and 15 mM (hyperglycaemic). Glucose uptake in the absence of inhibitors (control) was lowest at 1 mM glucose (18.4 ± 0.4 nmol/mg protein), increased at 5 mM (25.9 ± 0.3 nmol/mg protein) and was greatest at 10 mM glucose (39.7 ± 7.3 nmol/mg protein) and at 15 mM glucose (34.0 ± 2.7 nmol/mg protein) (n = 3) (Figs. 1a and 2a–c).Fig. 2


Apical and basolateral localisation of GLUT2 transporters in human lung epithelial cells.

Kalsi KK, Baker EH, Medina RA, Rice S, Wood DM, Ratoff JC, Philips BJ, Baines DL - Pflugers Arch. (2008)

Uptake of glucose (traced by [3H]-glucose) by non-polarised H441 cells incubated in culture medium containing 1 mM (a), 5 mM (b) or 15 mM (c) glucose. Cells were pre-incubated with vehicle (control), 500 μM phlorizin (PZ) or 1 mM phloretin (PT) before measurement of glucose uptake. Uptake experiments were performed at 37°C. Data are presented as mean ± SEM. **p < 0.01, significantly different from control
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2480509&req=5

Fig2: Uptake of glucose (traced by [3H]-glucose) by non-polarised H441 cells incubated in culture medium containing 1 mM (a), 5 mM (b) or 15 mM (c) glucose. Cells were pre-incubated with vehicle (control), 500 μM phlorizin (PZ) or 1 mM phloretin (PT) before measurement of glucose uptake. Uptake experiments were performed at 37°C. Data are presented as mean ± SEM. **p < 0.01, significantly different from control
Mentions: Glucose uptake by non-polarised cells was measured following incubation in culture medium containing a range of physiological glucose concentrations: 1 mM (hypoglycaemic); 5 mM (normoglycaemic); 10 mM (mildly hyperglycaemic) and 15 mM (hyperglycaemic). Glucose uptake in the absence of inhibitors (control) was lowest at 1 mM glucose (18.4 ± 0.4 nmol/mg protein), increased at 5 mM (25.9 ± 0.3 nmol/mg protein) and was greatest at 10 mM glucose (39.7 ± 7.3 nmol/mg protein) and at 15 mM glucose (34.0 ± 2.7 nmol/mg protein) (n = 3) (Figs. 1a and 2a–c).Fig. 2

Bottom Line: In non-polarised H441 cells, uptake of D: -glucose and deoxyglucose was similar.We could not conclusively demonstrate sodium/glucose transporter-mediated transport in non-polarised or polarised cells.We speculate that these transporters could contribute to glucose uptake/homeostasis in the human airway.

View Article: PubMed Central - PubMed

Affiliation: Centre for Ion Channel and Cell Signalling, Division of Basic Medical Sciences, St George's, University of London, Cranmer Terrace, London, SW17 0RE, UK.

ABSTRACT
Glucose concentrations of normal human airway surface liquid are approximately 12.5 times lower than blood glucose concentrations indicating that glucose uptake by epithelial cells may play a role in maintaining lung glucose homeostasis. We have therefore investigated potential glucose uptake mechanisms in non-polarised and polarised H441 human airway epithelial cells and bronchial biopsies. We detected mRNA and protein for glucose transporter type 2 (GLUT2) and glucose transporter type 4 (GLUT4) in non-polarised cells but GLUT4 was not detected in the plasma membrane. In polarised cells, GLUT2 protein was detected in both apical and basolateral membranes. Furthermore, GLUT2 protein was localised to epithelial cells of human bronchial mucosa biopsies. In non-polarised H441 cells, uptake of D: -glucose and deoxyglucose was similar. Uptake of both was inhibited by phloretin indicating that glucose uptake was via GLUT-mediated transport. Phloretin-sensitive transport remained the predominant route for glucose uptake across apical and basolateral membranes of polarised cells and was maximal at 5-10 mM glucose. We could not conclusively demonstrate sodium/glucose transporter-mediated transport in non-polarised or polarised cells. Our study provides the first evidence that glucose transport in human airway epithelial cells in vitro and in vivo utilises GLUT2 transporters. We speculate that these transporters could contribute to glucose uptake/homeostasis in the human airway.

Show MeSH