Inhibition of Active Sodium Transport in the Isolated Frog Skin

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Abstract
The isolated short-circuited frog skin, with Ringer soln. on both sides, was used to determine the effects of several groups of compounds on active Na transport. With this prepn. the electric current which can be drawn from the skin is equal to the net Na influx. The influx and outflux of Na and Cl were detd. by means of radioactive tracers. O2 consumption was measured in separate expts. Active Na transport (net Na influx) was inhibited by CNS, p-benzoquinone, sulfanilamide, p-toluene sulfonamide and 2,4-dinitrophenol. In some expts. the Na outflux was increased moderately, and the latter 3 compounds produced some increase in the permeability of the skin to Cl. Judging from the changes in electric current, active Na transport was also inhibited by acetylsulfonamide, Prontosil Red, p-aminobenzoic acid, p-nitrophenol and hydroquinone. Benzoic acid and 2,4,6-trinitro-phenol were ineffective. Substances which reduced O2 con-sumption reduced active Na transport, but others of the above which had no effect on O2 consumption or which increased it, also reduced active Na transport. In spite of the inhibitory effect of sulfonamides on active transport it is doubtful that carbonic anhydrase is involved. The inhibitory effect of 2,4-dinitrophenol indicates that high-energy phosphates are concerned in active Na transport in the frog skin.