A system and method of applying an electric field to the kidney of a subject can reduce renal salt and water retention through the process of electrophoresis. The system includes a first and a second electrode, at least of which is implantably associated with the kidney. The electric field can be controlled to affect the removal of a first constituent (e.g. sodium) from the kidney while the level of a second constituent (e.g. potassium) is maintained within normal physiological range.