1. Division of Nephrology, Department of Internal Medicine, University Medical Center Groningen, University of Groningen, PO Box 30.001 AA53, 9700 RB, Groningen, The Netherlands
2. Department of Cardiology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
3. Department of Clinical Pharmacology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
4. Department of Clinical Chemistry, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands