Non-electrolyte diffusion across the frog gastric mucosa under osmotic gradients

Serosal-to-mucosal and mucosal-to-serosal diffusion of 14C-labelled inulin, sucrose, erythritol and propionamide was compared with 3HHO diffusion in mucosae incubated with isosmotic solutions at both surfaces, as well as isosmotic solution at serosal surface and hyperosmotic solution at the mucosal surface. The use of a hyperosmotic solution at the mucosal surface significantly increases unidirectional diffusion fluxes of inulin and of sucrose. To a nonsignificant extent, it affects the fluxes of erythritol and propionamide and significantly reduces the 3HHO diffusion. A size increment of the diffusion path utilized by the larger molecules is proposed.