Effect of FeCl3 on ion transport in isolated frog skin
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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 (J13Na andJ31Na, respectively) and the influx and efflux of chloride (J13Cl andJ31Cl, respectively) across the epithelium. With normal Ringer's solution on both sides of the skin, addition of 10−3m FeCl3 to the external medium resulted in nearly complete inhibition of active Na transport (J13Na decreased from 1.30±0.14 to 0.10±0.04 μeq/cm2 hr (N=8)) and in appearance of active chloride transport in outward direction due to an 80% increase inJ31Cl. Average (J31Cl−J13Cl) 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 μeq/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 ofJ13Na 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.
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