Sugar transport in the LLC-PK1 renal epithelial cell line: similarity to mammalian kidney and the influence of cell density.

Cells of confluent cultures of the established pig renal epithelial line, LLC-PK1, accumulate alpha-methyl-D-glucoside against a concentration gradient. This transport system is strongly inhibited by phlorizin and 6-deoxy-D-glucose, moderately inhibited by phloretin, and only weakly inhibited by 3-0-methyl-D-glucose, paralleling the situation in mammalian kidney. The time courses for the uptake of alpha-methyl-D-glucoside and for the carrier-mediated but passive uptake of 3-0-methyl-D-glucose are identical to those seen in mammalian kidney. Subconfluent cultures of LLC-PK1 cells are unable to accumulate alpha-methyl-D-glucoside, and their transport of this glucose analog is less sensitive to phlorizin inhibition than is the transport system in confluent cultures. Transmission electron micrographs show that cells from subconfluent cultures lack the microvillous surface seen in cells from confluent cultures. Cell density is thus a factor in the occurrence of structural and functional differentiated properties related to transport in these cells.