CHARACTERISTICS OF SODIUM UPTAKE ACROSS THE BASOLATERAL MEMBRANE OF OXYNTIC CELLS

To characterize further serosal Na uptake into gastric oxyntic cells u nder resting conditions, cellular element concentrations were determin ed in isolated frog (Rana temporaria in) gastric mucosae using electro n microprobe analysis. The epithelia were kept short circuited in Ussi ng-type chambers, and element analysis was performed on freeze-dried c ryosections. After ouabain (10(-4) M), the [Na] in oxyntic cells incre ased within 30 to 60 minutes from approximately 25 to 100 mmol/kg wet wt, and [K] decreased similarly (from 100 to 25 mmol/kg wet wt). These changes occurred regardless of whether the basolateral incubation med ium contained HCO; or N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic a cid (HEPES) as buffers. When, prior to the addition of ouabain, 10(-3) M amiloride was applied to the serosal side to inhibit the Na-H antip orter, the ouabain-induced increase in cellular [Na] was prevented com pletely in HEPES-, but not in HCO3-Ringer. The data are compatible wit h the notion that Na is taken up by a Na-H antiporter and a Na-HCO3 sy mporter. Ar least under these experimental conditions, these transport ers seem to contribute substantially to basolateral Na uptake in oxynt ic cells.