Evidence for carrier-mediated uptake of sugars at the serosal side of lamb colon mucosa.

Sugar uptake through the basolateral membrane into epithelial cells was investigated in lamb colon stripped of serosa and muscle layers. Only the antiluminal surface of the mucosa was exposed to the incubtion medium. 2-Deoxy-D-glucose (2-DG) and 2-O-methyl-D-glucose (3-MG) were used as model substrates. Both sugars were taken up by a saturable process. Transport apparently occurred by facilitated diffusion. 2-DG uptake was inhibited by D-glucose and 3-MG, but not by D-galactose and alpha-methyl-D-glucoside and 3-MG uptake was inhibited by 2-DG and D-glucose but not by alpha-methyl-D-glucoside. Thus 2-DG, 2-MG and glucose appear to compete for a common transport mechanism. Carrier-mediated uptake of glucose through the basolateral membranes is probably important for the energy supply of colon epithelium.