, Volume 42, Issue 4, pp 345-356

Studies on chloride permeability of the skin ofLeptodactylus ocellatus: III. Na+ and Cl effect on electrical phenomena

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During their flux through the skin of the frogLeptodactylus ocellatus, Na+ and Cl interact with each other. This interaction gives rise to electrical phenomena which are studied in the present paper. The skin is mounted in Na2SO4 Ringer's with 115 mM Na+ on the inside, and a variety of outer solutions,. The osmolarity of all solutions is kept constant at 237.8 mosmol by adding sucrose. When the main anion used on the outside is SO 4 = the electrical potential difference (Δψ) rises steadily with the concentration of sodium (Na+)o up to 87 mV, which is reached at about 20mm. Thereafter Δψ remains constant. When the main anion is Cl it is observed that Δψ rises steadily with (NaCl)o with a slope similar to the curve obtained with SO 4 = (37 mV per decade), but with a lower intercept attributed to an inward Cl pumping which is characteristic of this frog species. At 2–9 mM (NaCl)o a Cl-specific channel is activated. Further increases of (NaCl)o produce a decrease of Δψ. The specificity of the activation of this site by monovalent cations and its use by monovalent anions is also studied.