Acidification of the bathing fluid by the skin of Rana pipiens in metabolic acidosis.

The skin of Rana pipiens can be shown to excrete H+ in an in vitro preparation. This H+ excretion is increased by placing the frog in metabolic acidosis. In addition, H+ excretion is increased by the presence of HCO-3-CO2 on the serosal or inside surface of the skin. Removal of Na+ from the outside bathing solution of the skin has no apparent effect on H+ excretion. Ouabain inhibits H+ excretion by the skin of acidotic frogs almost completely, in the absence of exogenous CO2. In the presence of 5% CO2 ouabain inhibits H+ excretion by 50%. In the acidotic frog skin the H+ excretion was reduced by abolishing the spontaneous potential difference. While in the normal skin there was no effect. When the P.d. was clamped at -10 to -100 mV there was no effect on H+ excretion, while there was a slight depression of H+ excretion when the P.d. was clamped at +10 to +100 mV (outside to inside the skin). In the presence of 5% CO2 there was a marked depression of H+ excretion when clamped at -10 to -100 mV in the normal skin. In metabolic acidosis there was a marked stimulation when clamped at -10 to -100 mV.