Effect of FeCl3 on ion transport in isolated frog skin

Summary The effect of addition of FeCl₃ to the media bathing the isolated skin ofRana pipiens was studied by measuring short-circuit current, transepithelial potential, and resistance, and by determining the influx and efflux of sodium (J ₁₃ ^Na andJ ₃₁ ^Na , respectively) and the influx and efflux of chloride (J ₁₃ ^Cl andJ ₃₁ ^Cl , respectively) across the epithelium. With normal Ringer's solution on both sides of the skin, addition of 10^–3 m FeCl₃ to the external medium resulted in nearly complete inhibition of active Na transport (J ₁₃ ^Na decreased from 1.30±0.14 to 0.10±0.04 eq/cm² hr (N=8)) and in appearance of active chloride transport in outward direction due to an 80% increase inJ ₃₁ ^Cl . Average (J ₃₁ ^Cl –J ₁₃ ^Cl ) obtained from means of 8 skins in 6 consecutive control and last 3 experimental periods was –0.17±0.04 and 0.38±0.05 eq/cm² hr, respectively. FeCl₃ added to external medium also induced substantial net chloride movement in outward direction when external medium contained Na-free choline chloride Ringer's or low ionic strength solution. Under the latter condition net Na movement was virtually eliminated by external FeCl₃. After addition of FeCl₃ to serosal medium there was delayed inhibition ofJ ₁₃ ^Na but no change in chloride fluxes. Immediate and profound changes in Na and Cl transport systems seen after external application of FeCl₃ indicate charge effects of Fe³⁺ on surface of apical cell membranes, possibly close to or in ion channels.