We have reported previously that in the presence of an osmotic gradient, facilitative glucose transporters (GLUTs) act as a transmembrane pathway for water flow. Here, we find evidence that they also allow water passage in the absence of an osmotic gradient. We applied the linear diffusion technique to measure the diffusional permeability (Pd) of tritiated water (3H-H2O) through plasma membranes of J774 murine macrophage-like cells. Untreated cells had a Pd of 30.9 +/- 1.8 microns/s; the inhibitors of facilitative glucose transport cytochalasin B (10 microM) and phloretin (20 microM) reduced that value to 15.3 +/- 1.8 (50%) and 11.0 +/- 0.7 (62%) microns/s, respectively. In contrast, no significant effect on Pd was observed in cells treated with dihydrocytochalasin B (Pd = 28.4 +/- 1.5 microns/s). PCMBS (3 mM) inhibited glucose uptake by greater than 95%, and 3H-H2O diffusion by approximately 30% (Pd = 22.9 +/- 1.5 microns/s). The combination of cytochalasin B plus pCMBS reduced Pd by about 87% (Pd = 3.9 +/- 0.3 microns/s). Moreover, 1 mM pCMBS did not affect the osmotic water permeability in Xenopus laevis oocytes expressing the brain/erythroid form of facilitative glucose transporters (GLUT1). These results indicate for the first time that about half of the total Pd of J774 cells may be accounted for by water passage across GLUTs. Hence, they highlight the multifunctional properties of these transporters serving as conduits for both water and glucose. Our results also suggest for the first time that pCMBS blocks glucose transport without affecting water permeation through GLUTs. Lastly, because pCMBS decreases the Pd of J774 cells, this suggests the presence in their plasma membranes of another protein(s) exhibiting water channel properties.
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1 November 1993
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November 01 1993
Role of facilitative glucose transporters in diffusional water permeability through J774 cells.
J D Loike,
J D Loike
Department of Physiology and Cellular Biophysics, Columbia University, New York, New York 10032.
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L Cao,
L Cao
Department of Physiology and Cellular Biophysics, Columbia University, New York, New York 10032.
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K Kuang,
K Kuang
Department of Physiology and Cellular Biophysics, Columbia University, New York, New York 10032.
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J C Vera,
J C Vera
Department of Physiology and Cellular Biophysics, Columbia University, New York, New York 10032.
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S C Silverstein,
S C Silverstein
Department of Physiology and Cellular Biophysics, Columbia University, New York, New York 10032.
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J Fischbarg
J Fischbarg
Department of Physiology and Cellular Biophysics, Columbia University, New York, New York 10032.
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J D Loike
Department of Physiology and Cellular Biophysics, Columbia University, New York, New York 10032.
L Cao
Department of Physiology and Cellular Biophysics, Columbia University, New York, New York 10032.
K Kuang
Department of Physiology and Cellular Biophysics, Columbia University, New York, New York 10032.
J C Vera
Department of Physiology and Cellular Biophysics, Columbia University, New York, New York 10032.
S C Silverstein
Department of Physiology and Cellular Biophysics, Columbia University, New York, New York 10032.
J Fischbarg
Department of Physiology and Cellular Biophysics, Columbia University, New York, New York 10032.
Online ISSN: 1540-7748
Print ISSN: 0022-1295
J Gen Physiol (1993) 102 (5): 897–906.
Citation
J D Loike, L Cao, K Kuang, J C Vera, S C Silverstein, J Fischbarg; Role of facilitative glucose transporters in diffusional water permeability through J774 cells.. J Gen Physiol 1 November 1993; 102 (5): 897–906. doi: https://doi.org/10.1085/jgp.102.5.897
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