Fax +41 61 306 12 34 E-Mail karger@karger.ch www.karger.com Original Paper Kidney Blood Press Res 2008;31:127–134 DOI: 10.1159/000124285 Lack of iNOS Impairs Endothelial Function in Endothelin-1 Transgenic Mice Thomas Quaschning a Florian Voss b, d Sophia Herzfeld d Katharina Relle d, e Philipp Kalk d, f Michael Godes d Thiemo Pfab d, f Annette Kraemer-Guth a Andreas W. Bonz c Franz Theuring d Jan Galle b Berthold Hocher d a Department of Nephrology, University Hospital of Freiburg, Freiburg, b Department of Nephrology and c Medizinische Klinik und Poliklinik I, University Hospital of Würzburg, Würzburg, d Center for Cardiovascular Research/Institute of Pharmacology and e Institute of Vegetative Physiology, Campus Mitte and f Department of Internal Medicine IV, Nephrology, Campus Benjamin Franklin, Charité, Berlin, Germany in ET+/+ iNOS–/– crossbred animals versus ET+/+ mice. Max- imum endothelium-dependent relaxation was enhanced in ET+/+ mice (95 8 5 vs. 78 8 5% of preconstriction in wild- type littermates; p ! 0.05). Additional knockout of iNOS led to a significant decrease of endothelium-dependent relax- ation in combined ET+/+ iNOS–/– animals (75 8 6%; p ! 0.05 vs. ET+/+ mice). Endothelium-independent relaxation was comparable among all groups. Maximum vascular contrac- tion to ET-1 was reduced in ET+/+ mice (33 8 4%), iNOS–/– mice (38 8 5%) and ET+/+ iNOS–/– mice (44 8 4%) to a sim- ilar extent as compared with wild-type littermates (66 8 4%; p ! 0.05). Conclusions: Our data show for the first time that in transgenic mice overexpressing human ET-1, additional knockout of iNOS results in impaired endothelium-depen- dent vasodilatation thus contributing to elevated blood pressure in ET+/+ iNOS–/– animals. Copyright © 2008 S. Karger AG, Basel Introduction The 21-amino-acid peptide endothelin-1 (ET-1) is pro- duced by the intact vascular endothelium and is known to be a potent vasoconstrictor [1] and mitogen in vivo and in vitro [2] . The biological effects of ET-1 are mediated via Key Words Nitric oxide  Endothelin  Endothelium  Relaxation  Vasoconstriction  Vasculature  Endothelium-dependent relaxation Abstract Background: Endothelin-1 (ET-1) is one of the most potent biologic vasoconstrictors. Nevertheless, transgenic mice overexpressing ET-1 exhibit normal blood pressure. We hy- pothesized that in states of ET-1 overproduction, the lack of counterregulatory mediators such as nitric oxide (NO), pro- duced by the inducible NO synthase (iNOS), may critically impair endothelial function and may result in blood pressure elevation. Methods: We generated crossbred animals of ET transgenic mice (ET+/+) and iNOS knockout mice (iNOS–/–) and evaluated blood pressure and endothelial function in these animals. Endothelium-dependent and -independent vascular function was assessed as relaxation/contraction of isolated preconstricted aortic rings to acetylcholine, sodium nitroprusside, and ET-1, alone or in the presence of BQ123 or BQ788. Results: Systolic blood pressure was similar in ET+/+, iNOS–/– and wild-type mice, but was significantly elevated Received: November 13, 2007 Accepted: February 11, 2008 Published online: April 7, 2008 Prof. Dr. Berthold Hocher Humboldt University of Berlin, University Hospital Charité Center for Cardiovascular Research and Institute for Pharmacology Hessischestrasse 3–4, DE–10115 Berlin (Germany) Tel. +49 30 450 514 098, Fax +49 30 450 514 938, E-Mail berthold.hocher@charite.de © 2008 S. Karger AG, Basel 1420–4096/08/0312–0127$24.50/0 Accessible online at: www.karger.com/kbr T.Q. and F.V. contributed equally to this work.