[Localization of chlorine barrier by transepithelial transient electric potentials in rana skin]

The localization of the outermost barrier to chloride influx in the abdominal skin of Leptodactylus ocellatus was investigated by a technique developed by Kidder et al. The method analyses the transient changes in transepithelial electrical potential differences produced when an impermeable anion (SO4(2) or gluconate) is rapidly replaced by Cl in the external bathing solution. The experimental results indicate that the Cl barrier is at the same level as the external Na barrier, that is, at the outward facing membrane of the cells of the stratum granulosum. Further experiments demonstrate that Br behaves like Cl, whereas I seems to behave as an impermeable anion, and that Na is needed for activating the anion permeation mechanism at the external barrier of the epithelium.