| Popis: |
The transport and intracellular accumulation of 1,5-anhydro-D-glucitol (AG) was studied in the human erythroleukemia cell line K-562 by gas chromatography-mass spectrometry in conjunction with liquid scintillation spectrometry. K-562 cells contained 106 +/- 6 nM/10(6) cells of free AG, primarily in the cytosol. Addition of physiologic amounts of AG to the extracellular medium resulted in rapid intracellular incorporation of AG, with a half-saturation time of 5 s. Intracellular accumulation was linear for 2 h and subsequently reached saturation. AG uptake was temperature and concentration dependent with an apparent Km of 127 mM. AG uptake and accumulation was not inhibited by fructose, fucose, galactose, mannose, glucose, or 3-O-methyl-D-glucose and was less affected by cytochalasin B or phloretin than that of 2-deoxyglucose. Phloridzin did not affect AG uptake but did inhibit 2-deoxyglucose uptake. Efflux of AG from K-562 cells depended on external AG concentration alone and was not affected by extracellular glucose concentration. Intracellular AG concentration decreased rapidly and reached zero within 10 min following removal of AG from the external medium. We therefore propose that both transport and countertransport of AG in K-562 cells are mediated by a specific carrier system. |
