Permeability of frog skin to choline.

An inward movement of choline can be demonstrated across isolated skins of Rana pipiens when the outside is bathed by a saline made with choline chloride. This is in contrast to an earlier report indicating that skins of R. esculenta are impermeable to choline. The flux was very small and independent of the active transport of sodium by the skins. For most experiments choline can be used as an "inert" replacement for sodium in this prepration.