Studies on chloride permeability of the skin of Leptodactylus ocellatus: I. Na+ and Cl- effect on passive movements of Cl-.

The outflux of chloride through the isolated skin (JCl31) of the South American frog Leptodactylus ocellatus (L.) is carried by a mechanism that saturates at high concentration of chloride on the inside, and is stimulated by the presence of Cl- in the outer solution (trans side). The presence of Na+ on the outside, by itself, does not increase JCl31. However, when JCl31 is already increased by chloride on the trans side, the addition of Na+ produces a significant further increase. At low concentration of Cl- on the outside JCl31 is carried by an exchange diffusion mechanism. At high concentrations of Cl- outside, JCl31 proceeds through a route which involves changes in electrical parameters. The results suggest that both mechanisms are located on the cell membranes and, therefore, that the fluxes would cross through the cytoplasm of the cells. Na+ stimulates the second mechanism only.