The Role of CI‐ and other Anions in Active Na+ Transport in Isolated Frog Skin

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Abstract
Huf, E. G. The role of CI and other anions in active Na* transport in isolated frog skin. Acta physiol. scand. 1972. 84. 366–381.Skins of several amphibian species were kept between hemi‐chambers in solutions of identical SO42 Ringers' solutions with, or without mannito! (SM, S). When steady state was reached the SO‐i2˜ ions were replaced by equivalent amounts of one of the following anions (A): Cl−, HCO3k, NO3. Replacements were made in sequence, on the outside (o), the inside (i), and both sides of the skin, with periods of SO42 solutions on both sides between the several phases. In other experiments skin pairs were set up for simultaneous Na 24 and CI35 influx and out‐flux measurements. In all experiments, measurements on short circuit current (SCC) and open skin PD (E) were made, and from this total skin conductance (GT) data were calculated, as were values for E\a and Gaxa‐ From these data it is concluded that CI; (with SM0) leads to stimulation of Na* influx and net Na* flux resulting from epithelial swelling; increase in SCC; E; GT; E\a Gaxa‐The order of effectiveness of Af on electrical parameters was Cl− > NO3 > HCO3. Cl0 (with Clf) resulted in: a) “shunting” of Exa; b) depression of Na* influx, of SCC, E, Exa, G\\a; c) Cl0 (with SMj) seemed to stimulate Na* influx, but the flux data were as yet inconclusive. There were marked skin species differences. Best recoveries of starting values were obtained with skins of R. esculenta. Increases or decreases in Na* influx did not correlate with changes in Na* outflux, Cl− influx and Cl− outflux. Possible sites of A”‐membrane interactions involving the Na* transport system are discussed. Work by others is confirmed that in skins of R. esculenta, bathed in SO‐12 Ringer's with 4 mM Cl−, Cl− is actively transported in the inward direction at a level of approximately 109rof the active inward Na* transport.

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