1. Cardiorenal Research Laboratory, Department of Cardiovascular Medicine, Mayo Clinic , 200 1st Street SW, Rochester, MN 55905 , USA
2. Department of Physiology and Biomedical Engineering , Mayo Clinic 200 1st St SW, Rochester MN 55905 , USA
3. Institute of Physiology, University of Wuerzburg , Roentgenring 9, D-97070 Wuerzburg , Germany
4. Department of Medicine and Surgery, University of Parma , Via Gramsci 14, 43126 Parma , Italy