1. From the Department of Pathology and Medical Biology (W.B.W.H.M., G.M.M., H.v.G.), University Medical Center Groningen and University of Groningen, Groningen, The Netherlands; Department of Physiology (Q.X., J.G.J.H.), Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands; and the Cardiovascular Research Center (K.K., S.E.), Department of Physiology, Temple University School of Medicine, Philadelphia, Pa.