Premium
Water transport by the Na + /glucose cotransporter under isotonic conditions Proceedings of a meeting held in Paris, 27–30 April, 1997, as a tribute to Jacques Bourguet. *
Author(s) -
Zeuthen Thomas,
Meinild AnneKristine,
Klaerke Dan A,
Loo Donald DF,
Wright Ernest M,
Belhage Bo,
Litman Thomas
Publication year - 1997
Publication title -
biology of the cell
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.543
H-Index - 85
eISSN - 1768-322X
pISSN - 0248-4900
DOI - 10.1111/j.1768-322x.1997.tb01027.x
Subject(s) - cotransporter , water transport , biophysics , osmosis , pipette , biology , xenopus , intracellular , gramicidin , glucose transporter , membrane , biochemistry , water flow , sodium , chemistry , organic chemistry , gene , insulin , engineering , endocrinology , environmental engineering
Solute cotransport in the Na + glucose cotransporter is directly coupled to significant water fluxes. The water fluxes are energized by the downhill fluxes of the other substrates by a mechanism within the protein itself. In the present paper we investigate the Na + glucose cotransporter expressed in Xenopus oocytes. We present a method which allows short‐term exposures to sugar under voltage clamp conditions. We demonstrate that water is cotransported with the solutes despite no osmotic differences between the external and intracellular solutions. There is a fixed ratio of 195:1 between the number of water molecules and the number of Na + ions transported, equivalent to 390 water molecules per glucose molecule. Unstirred layer effects are ruled out on the basis of experiments on native oocytes incubated with the ionophores gramicidin D or nystatin.