Na+-dependent co-transport of alpha-methyl D-glucoside across the mucosal border of rabbit descending colon.

(1) The uptake and bidirectional fluxes of 1-alpha-methyl D-glucoside were studied in isolated rabbit colonic mucosa. (2) The uptake of alpha-methyl D-glucoside was linear over the first 30 min and reached maximum after 1 h; was a saturable function of sugar concentration and was Na+-dependent. (3) An increase in sugar uptake across the mucosal border and net transepithelial sugar flux across sheets of colon was observed in the presence of 10(-4) M amiloride. (4) Phlorizin (10(-4) M) inhibited sugar uptake into the tissue water and abolished net sugar flux. Amiloride-stimulated sugar uptake was also abolished by 10(-4) M phlorizin. (5) Ouabain (10(-4) M) prevented the effect of amiloride on sugar uptake and inhibited sugar uptake into the tissue. (6) These results corroborate the findings of Henriques de Jesus et al. (Henriques de Jesus, C., Da Gracia Emilio, M. and Santos, M.A. Gastroenterol. Clin. Biol. 3, 172-173) who found a sugar-dependent increase in short-circuit current in colonic mucosa exposed to amiloride.