1. Department of Pharmacology, New York Medical College, Valhalla, New York 10595
2. Laboratory of Molecular Physiology and Biophysics, Renal Division, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, 75 Francis Street, Boston, Massachusetts 02115
3. Department of Cellular and Molecular Physiology, Yale University School of Medicine, 333 Cedar Street, New Haven, Connecticut 06520-8026