Contribution of mucosal chloride to chloride in toad bladder epithelial cells

Epithelial cells were scraped from the bladders of toads of the species Bufo marinus obtained from the Dominican Republic. These epithelial cells exchanged their chloride virtually completely with 36Cl i; the medium within 60 min. Of this chloride, about 93% came from the serosal medium. The approximately 20 mmole/kg dry wt of chloride which equilibrates with 36Cl in the mucosal medium was still present when choline replaced sodium in the medium in the presence of amiloride (10(-4) M) and was almost all readily removed by rapid washing of the mucosal surface immediately prior to analysis. These observations suggest that little chloride of mucosal origin is truly intracellular. This conclusion is supported by the fact that after vasopressin the increased cellular chloride was not of mucosal origin.