KALTENBACH, J.C.: ATPase immunoreactivity and lectin binding in gills of larval amphibians and fish

Strong Na⁺/K⁺ ATPase activity is a characteristic of chloride cells (mitochondria-rich cells) in fish gills. Such cells have an important role in ion transport. To determine if similar cells are also present in the internal gills of amphibian tadpoles, paraffin sections of gills, and of other tissues, were prepared from representative larval stages of the bullfrog and leopard frog (Rana catesbeiana and Rana pipiens) and from gills of the freshwater goldfish (Carassius auratus). The following techniques were then applied: 1) histochemical staining with four peroxidase-conjugated lectins for specific terminal sugars of glycoconjugates and 2) immunostaining with antibody to the ALPHA subunit of avian Na⁺/K⁺ ATPase. Certain epithelial cells in gills of both tadpoles and fish stained intensely with each of the four lectins (PNA for galactose, SBA for N-acetylgalactosamine, WGA for N-acetylglucosamine, and con A for mannose). However, ATPase reactivity was different in the gills of the two types of animals. In contrast to the strong ATPase immunostaining in chloride cells of goldfish gills, little or no immunoreactivity was detected in amphibian gills. Yet ATPase staining was strong in the few flask cells present within the epidermis of tadpole skin as well as in the tubules of the tadpole pronephric kidney. In conclusion, lectin staining indicated that specific terminal sugars on glycoconjugates are similar in certain epithelial cells of gills of both tadpoles and fish. Moreover, the strong ATPase immunoreactivity in the tadpole pronephric kidney (as in chloride cells of fish gills), plus the very weak activity in tadpole gills, suggests that the pronephric kidney may play a more important role than the gills with respect to ion transport in larval amphibians.