Gr. Kracke et al., IDENTIFICATION OF A SORBITOL PERMEASE IN HUMAN ERYTHROCYTES, The American journal of physiology, 266(2), 1994, pp. 30000343-30000350
Sorbitol, a polyol derived from glucose by the enzyme, aldose reductas
e, is a common organic solute in many cells. It plays a role in the os
motic regulation of epithelial cells and in the pathology of uncontrol
led diabetes. To learn more about sorbitol transport, we measured D-[C
-14]sorbitol influx in human erythrocytes. Sorbitol influx at 37 degre
es C was a linear function of sorbitol concentration over the range of
0.05-100 mM. The activation energy for sorbitol influx was 10.0 kcal/
mel, and the Q(10) over the range 10-50 degrees C was 1.8, higher tha
n predicted for diffusion through an aqueous pore. Glucose transport i
nhibitors either had no effect (1 mM phloridzin) or minimally inhibite
d (similar to 35% inhibition by 10 mu M cytochalasin B or 250 mu M phl
oretin) sorbitol influx. Influx was stimulated twofold by 0.5 mM p-chl
oromercuribenzoic acid, an inhibitor of glucose transport, and this wa
s reversed by 2 mM dithiothreitol. Sorbitol influx was neither Na depe
ndent nor sensitive to changes in cell volume. Glucose, fructose, mann
itol, myo-inositol, and gluconate, at four- to fivefold molar excesses
over sorbitol, did not inhibit its influx. We conclude that there is
a specific sorbitol transport pathway in human erythrocytes similar to
the sorbitol permease in renal epithelial cells.