Inositol transport in mouse embryonic stem cells.
The uptake of myo-inositol by mouse embryonic stem (ES) cells was measured using [2-(3)H]myo-inositol. Uptake of myo-inositol by ES cells occurred in a mainly saturable, sodium-, time- and temperature-dependent manner, which was inhibited by glucose, phloridzin and ouabain. Self inhibition by inositol was much greater than inhibition by glucose indicating that transport was not occurring via a sodium-dependent glucose transporter. Uptake rate was much greater than efflux rate indicating a mainly unidirectional transport mechanism. Estimated kinetics parameters for sodium-dependent inositol uptake were a K m of 65.1 +/- 11.8 micromol L(-1) and a V max of 5.0 +/- 0.59 pmol microg protein(-1) h(-1). Inositol uptake was also sensitive to osmolality; uptake increased in response to incubation in hypertonic medium indicating a possible role for inositol as an osmolyte in ES cells. These characteristics indicate that myo-inositol transport in mouse ES cells occurs by a sodium-dependent myo-inositol transporter protein.
Higgins
B D
BD
Department of Physiology, National University of Ireland, Galway.
Kane
M T
MT
D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002478:Cells, Cultured; D004622:Embryo, Mammalian / Q000166:cytology*; D005947:Glucose / Q000378:metabolism; D007294:Inositol / Q000378:metabolism*; D007700:Kinetics; D051379:Mice; D009994:Osmolar Concentration; D010693:Phloretin / Q000494:pharmacology; D010695:Phlorhizin / Q000494:pharmacology; D012964:Sodium / Q000378:metabolism / Q000494:pharmacology; D013234:Stem Cells / Q000187:drug effects / Q000378:metabolism*; D013696:Temperature; D013997:Time Factors
D007294:Inositol; D012964:Sodium; D010695:Phlorhizin; D005947:Glucose; D010693:Phloretin