Enzyme cytochemical and immunocytochemical studies of flask cells in the amphibian epidermis.

The localization of oxidoreductases and transport enzymes in flask cells of the amphibian epidermis was studied at the light-microscopic level. In these cells, the deposition of cytochemical reaction products was very similar to that found in fish epidermal ionocytes, thus demonstrating histochemical similarities between these two types of cells. The present histochemical results revealed high levels of activity of alkaline phosphatase (ALPase), potassium-dependent nitrophenylphosphatase (K+-p-NPPase) and carbonic-anhydrase isozymes (CA-I and CA-II) in the apical region of the flask cells, indicating that enzyme zonation may be the main site of the ion pumping.