SOME MORPHOLOGICAL ASPECTS OF ACTIVE SODIUM TRANSPORT* : The Epithelium of the Frog Skin

A method was experimentally tested which allows simultaneous morphological and bioelectrical studies of a tissue that performs active sodium transport, i.e., the isolated, surviving frog skin. In a four cell lucite chamber with four separate electric potential and current circuits, skin specimens for morphological observation (light and electron microscopy) were fixed in situ in well-defined functional states. The rate of active sodium transport through the epithelium of Rana temporaria skin was modified by changing the strength of the electric current passed through the specimens. A marked, reversible swelling of the outermost layer of the stratum granulosum was observed during short circuiting of the skin compared to the homogeneous appearance of the epithelium under open circuit conditions. Doubling the ingoing current led to an additional small increase of the swelling or the appearance of islets of cell necrosis in the same layer. There were signs of a slight shrinkage of the underlying cell layers. The observations are discussed in the light of previous bioelectrical and morphological observations.