Active transport of ions by the gastric mucosa of the rabbit foetus.

1. The short-circuit current and absolute fluxes of Na(+) and Cl(-) across the gastric mucosa of the 28-day rabbit foetus have been measured in vitro.2. Substitution of Na(+) in the solution bathing the mucosal surface by choline ion or K(+) resulted in a 70% decrease in short-circuit current which was reversed when Na(+) was restored to the mucosal solution. The portion of the short-circuit current dependent on the presence of Na(+) in the mucosal solution was found to be equivalent to the net flux of Na(+) from mucosa to serosa.3. The net flux of Cl(-) from serosa to mucosa was compared with the short-circuit current persisting when Na(+) had been replaced in the mucosal solution. Averaged results from sixteen experiments indicated that the net flux of Cl(-) was equivalent to 166% of the Na(+) independent short-circuit current.4. The results indicated that the component of short-circuit current associated with acid secretion was independent of the presence of Na(+) in the mucosal solution.5. The small scale of the experiments and the secretion of mucus by the preparation did not permit successful simultaneous measurement of H(+) secretion and short-circuit current.6. Replacement of Cl(-) by SO(4) (2-) or glucuronate in the solutions on both sides did not result in a reversal or decrease in magnitude of the Na(+) independent short-circuit current, even after allowing time for the tissue to become depleted of Cl(-). It is suggested that a non-specific active anion transport was occurring.