[1] Univ Zurich Hosp, Dept Cardiol, Cardiovasc Cntr, CH-8091 Zurich, Switzerland
[2] UCL, Vasc Physiol Unit, London, England
[3] Univ Zurich, Inst Physiol, Zurich, Switzerland
[4] Univ Zurich Hosp, Inst Clin Chem, CH-8091 Zurich, Switzerland
[5] F Hoffmann La Roche & Co Ltd, Clin Dev, CH-4002 Basel, Switzerland