Abstract
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.
| Original language | English |
|---|---|
| Journal | Biology of the Cell |
| Volume | 89 |
| Issue number | 5-6 |
| Pages (from-to) | 307-12 |
| Number of pages | 6 |
| ISSN | 0248-4900 |
| Publication status | Published - 1997 |