Transepithelial transport in cell culture: D-glucose transport by a pig kidney cell line (LLC-PK1).

The pig kidney cell line LLC-PK1 cultured on a collagen coated membrane filter formed a continuous sheet of oriented asymmetrical epithelial cells joined by occluding junctions. A transepithelial electrical potential (PD) and short-circuit current (SCC) were dependent on the presence of Na and sugar in the apical bathing solution. In the presence of 5.5 mM D-glucose, a PD of 2.8 mV. apical surface negative a SCC of 13 microA cm-2 and transepithelial resistance of 211 ohm.cm2 were recorded. The SCC was promptly reduced by the addition of phlorizin to the apical bath but unaffected when placed in the basolateral bath. The effect on SCC of various sugars was compared by the concentrations required for half-maximal SCC: 0.13 mM beta-methyl-D-glucoside, 0.28 mM D-glucose, 0.65 mM alpha-methyl-D-glucoside, 0.77 mM 6-deoxy-D-glucose, 4.8 mM D-galactose, and 29 mM 3-O-methyl-glucose. When [Na] was reduced, the concentration of D-glucose required for half-maximal SCC increase. Isotopically labeled 3H and 14C D-glucose were used to simultaneously determine bidirectional fluxes; a resultant net apical-to-basolateral transport was present and abolished by phlorizin. The transported isotope cochromatographed with labeled D-glucose, indicating negligible metabolism of transported glucose. The pig kidney cell line, LLC-PK1, provides a cell culture model for the investigation of mechanisms of transepithelial glucose transport.