Klotho-hypomorphic (Klotho hm ) mice suffer from renal salt wasting and hypovolemia despite hyperaldosteronism. The present study explored the effect of Klotho on renal Na + /K + ATPase activity. According to immunohistochemistry and confocal microscopy Na + /K + ATPase protein abundance in isolated collecting ducts was lower in Klotho hm mice than in their wild type littermates (Klotho +/+ ). Analysis with dual electrode voltage clamp recording showed that expression of Klotho in Xenopus oocytes increased the Na + /K + ATPase pump current. Treatment of Xenopus oocytes with Klotho protein similarly increased the pump current. In conclusion, Klotho increases the membrane abundance and activity of the Na + /K + ATPase. Decreased Na + /K + ATPase activity could thus contribute to the volume-depletion of klotho hm mice.Na+/K+ ATPase alpha-1 physically interacts with Klotho by anti bait coimmunoprecipitation (View interaction).