Abstract
1. Isolated midguts of the freshwater snail Biomphalaria glabrata were mounted in an incubation chamber in saline containing 2 mM glucose and perfused with the same solution. External and internal media were continuously gassed with carbogen gas (95% O-2, 5% CO2). In order to measure the dux rates of glucose [C-14]glucose was applied in the perfusion medium or in the incubation medium. Net fluxes of glucose were calculated as the differences between unidirectional in- and effluxes. 2. A directed net flux from the mucosal to the serosal side of the intestine 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 reduced by the presence of metabolic inhibitors, cyanide (1 mM) and dinitrophenol (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 serosal 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 that glucose transport is secondary active and coupled to Na+-transport.