Sodium- potassium-activated adenosine triphosphatase and osmotic regulation by fishes.

JAMPQL, LEE M., AND FRANKLIN H. EPSTEIN. Sodiumpotassiumactivated adenosine triphosphatase and osmotic regulation by fishes. Am. J. Physiol. 218(2) : 607-611. 1970.-The specific activity of sodiumpotassium-activated adenosine triphosphatase is high in the gills of sa1twater teleosts, and low in the gills of elasmobranchs and freshwater teleosts. The activity of NaK-ATPase in gill filaments and intestinal mucosa doubled when freshwater eels (AnguiZlu rostrata) were adapted to seawater for 2-3 weeks. A paradoxical finding was the high specific activity of NaK-ATPase in theaglomerular kidney of Luphius americanzls, reminiscent of the ATPase content of certain secretory organs, NaK-ATPase in rectal gland of Squalus acanthim was extremely high. The data indicate that NaK-ATPase activity varies with sodium transport in several organs of teleost and elasmobranch under differing circumstances of osmotic stress. The enzyme is likely, therefore, to play an important role in the active transport of sodium across epithe1ia1 membranes and the adjustment of marine animals to their environment.