1. From the Department of Internal Medicine-Nephrology (H.S., W.-T.H., M.T., I.G., G.G., T.M., J.H., R.K.), Philipps-University, Marburg; Department of Physiology (S.E.W., C.d.W.), University of Lübeck; Institute of Physiology (R.S.), University of Rostock; and Max-Delbrück-Centrum for Molecular Medicine (L.V., V.G., M.B.), Berlin-Buch, Germany.