Uptake of D-mannoheptulose by rat erythrocytes, hepatocytes and parotid cells

D-[H-3]mannoheptulose (or D-[1-C-14] mannoheptulose) net uptake was measure d in rat erythrocytes, parotid cells and hepatocytes. In the erythrocytes a nd parotid cells, the intracellular distribution space of the heptose (0.1 mM) represented only about 1 and 13%, respectively, of the intracellular (H OH)-H-3 space. In hepatocytes, however, it amounted to approximately 45% of the intracellular 3HOH space. In all cases, the apparent distribution spac e of D-[H-3]-mannoheptulose hexaacetate largely exceeded that of unesterifi ed D-[3H]mannoheptulose. Relative to the intracellular water space, the gen eration of acidic metabolites (expressed as an apparent distribution space) from radioactive D-mannoheptulose was one order of magnitude lower in paro tid cells (less than or equal to3%) than in hepatocytes (greater than or eq ual to 20%). These findings are compatible with the hypothesis that D-manno heptulose is transported into cells mainly, if not exclusively, at the inte rvention of GLUT2.