Characteristics of sorbitol uptake in rat glial primary cultures

Uptake of [U-14C]sorbitol was studied in astrogliarich rat primary cultures. Initial rate of sorbitol uptake is proportional to sorbitol concentration between 20 microM and 400 mM. Sorbitol transport is not inhibited by glucose, fructose, and a variety of structurally related polyols, or by cytochalasin B, an inhibitor of glucose transport. Phloretin, phlorizin, filipin, and n-hexanol, all compounds that alter the properties of biological membranes, and the sulfhydryl reagent p-chloromercuribenzoate inhibit sorbitol uptake to various degrees. Variation in the concentrations of extracellular Na+ and K+ does not affect transfer of sorbitol across the cell membrane. It is concluded that sorbitol is taken up into glial cells by a diffusion process, not involving a carrier and probably not through the lipid bilayer, but through a proteinaceous channel-like structure.