Effect of ketotifen on Na-K-ATPase activity. A, Villus cells. Na-K-ATPase activity that was significantly reduced in the villus cells during chronic enteritis was reversed by ketotifen treatment. B, Crypt cells. Na-K-ATPase activity was significantly elevated in the crypt cells from the chronically inflamed intestine and this stimulation was reversed by ketotifen treatment. Na-K-ATPase activity was unaffected in the crypt cells from normal intestine.