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Mobility of ions, sugar, and water in the cytoplasm of Xenopus oocytes expressing Na(+)-coupled sugar transporters (SGLT1).
Zeuthen T
,
Zeuthen E
,
Klaerke DA
.
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A model was set up to study water transport in membrane proteins expressed in Xenopus oocytes. The model was tested experimentally using human and rabbit Na+-glucose cotransporters (SGLT1), and was used to explain controversies regarding unstirred layer effects. Cotransport of Na+, sugar and water was monitored by two-electrode voltage clamp and online measurements of oocyte volume. The specific resistance of the oocytecytoplasm was found by means of microelectrodes to be 263 +/- 91 Omega cm (S.D., n = 52), or 2.5 times that of Kulori medium, in agreement with reported values of intracellular ion concentrations and diffusion constants. Osmotically induced volume and resistance changes were compatible with a model of the oocyte in which 37 +/- 17 % (S.D., n = 66) of the intracellular volume acts as a free solution while the remainder is inert, being occupied by organelles, etc. The model explains the results of several types of experiments: rapid changes in rates of water cotransport induced by changes in clamp voltage followed by osmotic equilibration in sugar-free conditions; volume changes induced by Na+ transport via the ionophore gramicidin; and uphill water transport. Ethanol (0.5 %) induced a marked swelling of the oocytes of about 16 pl x s(-1). If the specific inhibitor of SGLT1 phlorizin is added from stock solutions in ethanol, the effect of ethanol obfuscates the effects of the inhibitor. We conclude that the transport parameters derived for water cotransport by the SGLT1 can be attributed to the protein residing in the plasma membrane with no significant influences from unstirred layer effects.
Allbritton,
Range of messenger action of calcium ion and inositol 1,4,5-trisphosphate.
1992, Pubmed,
Xenbase
Allbritton,
Range of messenger action of calcium ion and inositol 1,4,5-trisphosphate.
1992,
Pubmed
,
Xenbase
Barish,
A transient calcium-dependent chloride current in the immature Xenopus oocyte.
1983,
Pubmed
,
Xenbase
Baumgartner,
Two-microelectrode voltage clamp of Xenopus oocytes: voltage errors and compensation for local current flow.
1999,
Pubmed
,
Xenbase
Chen,
Thermodynamic determination of the Na+: glucose coupling ratio for the human SGLT1 cotransporter.
1995,
Pubmed
,
Xenbase
Cole,
ELECTRIC IMPEDANCE OF SUSPENSIONS OF ARBACIA EGGS.
1928,
Pubmed
Cole,
ELECTRIC IMPEDANCE OF SUSPENSIONS OF SPHERES.
1928,
Pubmed
Dascal,
Xenopus oocyte resting potential, muscarinic responses and the role of calcium and guanosine 3',5'-cyclic monophosphate.
1984,
Pubmed
,
Xenbase
Dascal,
The use of Xenopus oocytes for the study of ion channels.
1987,
Pubmed
,
Xenbase
Duquette,
Local osmotic gradients drive the water flux associated with Na(+)/glucose cotransport.
2001,
Pubmed
,
Xenbase
Fushimi,
Low viscosity in the aqueous domain of cell cytoplasm measured by picosecond polarization microfluorimetry.
1991,
Pubmed
Hediger,
Expression cloning and cDNA sequencing of the Na+/glucose co-transporter.
,
Pubmed
,
Xenbase
HODGKIN,
The mobility and diffusion coefficient of potassium in giant axons from Sepia.
1953,
Pubmed
Kusano,
Cholinergic and catecholaminergic receptors in the Xenopus oocyte membrane.
1982,
Pubmed
,
Xenbase
Kushmerick,
Ionic mobility in muscle cells.
1969,
Pubmed
Lapointe,
The presence of local osmotic gradients can account for the water flux driven by the Na+-glucose cotransporter.
2002,
Pubmed
Leikin,
Hydration forces.
1993,
Pubmed
Loo,
Cotransport of water by the Na+/glucose cotransporter.
1996,
Pubmed
,
Xenbase
Lotan,
Adenosine-induced slow ionic currents in the Xenopus oocyte.
1982,
Pubmed
,
Xenbase
Luby-Phelps,
Hindered diffusion of inert tracer particles in the cytoplasm of mouse 3T3 cells.
1987,
Pubmed
Luby-Phelps,
A novel fluorescence ratiometric method confirms the low solvent viscosity of the cytoplasm.
1993,
Pubmed
MacAulay,
Water transport by the human Na+-coupled glutamate cotransporter expressed in Xenopus oocytes.
2001,
Pubmed
,
Xenbase
Meinild,
The human Na+-glucose cotransporter is a molecular water pump.
1998,
Pubmed
,
Xenbase
Meinild,
Water transport by the renal Na(+)-dicarboxylate cotransporter.
2000,
Pubmed
,
Xenbase
Meinild,
Bidirectional water fluxes and specificity for small hydrophilic molecules in aquaporins 0-5.
1998,
Pubmed
,
Xenbase
Palmer,
Distribution of Na+, K+ and Cl- between nucleus and cytoplasm in Chironomus salivary gland cells.
1977,
Pubmed
Pauly,
Dielectric properties and ion mobility in erythrocytes.
1966,
Pubmed
Päuser,
Estimation of water content and water mobility in the nucleus and cytoplasm of Xenopus laevis oocytes by NMR microscopy.
1995,
Pubmed
,
Xenbase
Quick,
Neutralization of a conserved amino acid residue in the human Na+/glucose transporter (hSGLT1) generates a glucose-gated H+ channel.
2001,
Pubmed
,
Xenbase
Sehy,
Water and lipid MRI of the Xenopus oocyte.
2001,
Pubmed
,
Xenbase
Terasaki,
Changes in organization of the endoplasmic reticulum during Xenopus oocyte maturation and activation.
2001,
Pubmed
,
Xenbase
Zampighi,
A method for determining the unitary functional capacity of cloned channels and transporters expressed in Xenopus laevis oocytes.
1995,
Pubmed
,
Xenbase
Zeuthen,
Isotonic transport by the Na+-glucose cotransporter SGLT1 from humans and rabbit.
2001,
Pubmed
,
Xenbase
Zeuthen,
Passive water transport in biological pores.
2002,
Pubmed
Zeuthen,
Cotransporters as molecular water pumps.
2002,
Pubmed
,
Xenbase
Zeuthen,
Cotransport of K+, Cl- and H2O by membrane proteins from choroid plexus epithelium of Necturus maculosus.
1994,
Pubmed
Zeuthen,
Cotransport of H+, lactate and H2O by membrane proteins in retinal pigment epithelium of bullfrog.
1996,
Pubmed
Zeuthen,
Relations between intracellular ion activities and extracellular osmolarity in Necturus gallbladder epithelium.
1982,
Pubmed
Zeuthen,
Water transport by the Na+/glucose cotransporter under isotonic conditions.
1997,
Pubmed
,
Xenbase
Zeuthen,
Molecular mechanisms for passive and active transport of water.
1995,
Pubmed
Zeuthen,
Water permeability of ventricular cell membrane in choroid plexus epithelium from Necturus maculosus.
1991,
Pubmed
