Amiloride, Animals, Calmodulin, Carrier Proteins, Cytosol, Genetic Vectors, Humans, Hydrogen-Ion Concentration, Kinetics, L Cells, Mice, Plasmids, Restriction Mapping, Sodium-Hydrogen Exchangers, Sulfonamides, Tetradecanoylphorbol Acetate, Transfection, Tumor Cells, Cultured