Efflux of chloride through cell surfaces of frog gastric mucosa

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Abstract
Concentration, effluxes, and exchangeable chloride were studied in the isolated frog gastric mucosa. The tissue chloride, 51.6 ± 0.7 (se) mm/kg wet wt, is totally exchangeable. The tissue chloride concentration increases to 68.0 ± 2 2 (se) mm/kg wet wt after incubation between two chloride solutions. Using sulfate secretory solution this value became 66.9 ± 1.3 (se) mm/kg wet wt. Using sulfate nutrient solution a decrease to 126 ± 1.1 (se) mm/kg wet wt was observed. Tissue chloride effluxes were described by two exponentials; one (extracellular chloride) had a time constant of 117 ± 04 (se) hr–1; the other (cellular chloride) had a time constant of 1.13 ± 0.07 (se) hr–1. The ratio of the effluxes through both surfaces, ΔAm/ΔAs was 1.59 ± 0.16 (se) in mucosae maintained between sulfate solutions. This ratio increases to 2.13 ± 0.10 (se) by the use of histamine in both solutions or decreases to 0.51 ± 0.05 (se) by the use of chloride solutions. It is proposed that a) there exists chloride passive diffusion through both surfaces of the cellular membrane, b) the barrier sensitive to histamine is close to the mucosal surface, where the active transport of chloride is located, and c) a barrier requiring exchange of chloride is located close to the serosal face of the cells.