GLUCOSE-TRANSPORT ACROSS THE INTESTINAL WALL OF THE FRESH-WATER SNAILBIOMPHALARIA-GLABRATA

1. Isolated midguts of the freshwater snail Biomphalaria glabrata were mounted in an incubation chamber in saline containing 2 mM glucose an d perfused with the same solution. External and internal media were co ntinuously gassed with carbogen gas (95% O-2, 5% CO2). In order to mea sure the dux rates of glucose [C-14]glucose was applied in the perfusi on medium or in the incubation medium. Net fluxes of glucose were calc ulated as the differences between unidirectional in- and effluxes. 2. A directed net flux from the mucosal to the serosal side of the intest ine was demonstrated (mucosal to serosal = 50 +/- 10 nmol cm(-2)hr(-1) (N = 6) serosal to mucosal 7 +/- 1 nmol cm(-2)hr(-1)(N = 6), net flux = 43 nmol cm(-2) hr(-1)). 3. The active transport of glucose was reduc ed by the presence of metabolic inhibitors, cyanide (1 mM) and dinitro phenol (1 mM) on the mucosal as well as on the serosal side. Ouabain ( 1 mM) inhibited the transport rate only when it was added on the seros al side. Amiloride (1 mM) had no effect on the transport rate whether added on the mucosal or on the serosal side. 4. Inhibition of glucose transport by oubain, a specific inhibitor of Na+/K+-ATPase, suggests t hat glucose transport is secondary active and coupled to Na+-transport .