Oral Abstract Session: Translational science

Abstract

301 Sustained Hypertension Despite Endothelium-Specific Reintroduction of Functionally Active eNOS in eNOS-Deficient Mice T Suvorava, VT Dao, M Oppermann, G Kojda Institute of Pharmacology and Clinical Pharmacology, University Hospital, Duesseldorf, Germany Topic: Hypertension Purpose: Several studies have shown that eNOS-deficient mice (eNOS-/-) have higher blood pressure than wild-type mice. It is frequently assumed that hypertension in eNOS-/is caused by the lack of endothelium-derived nitric oxide and the resulting increase in arterial tone and peripheral resistance. We sought to investigate whether endothelial-specific targeting of eNOS introduced in eNOS-/can normalize aortic reactivity and blood pressure. Methods:Transgenic mice carrying bovine eNOS (eNOSbovþ) have been generated on C57Bl/ 6 background using the endothelium-specific Tie-2 promotor. By breeding these mice with eNOS knockouts (eNOS-/-), mice that only express eNOSbov (eNOS-/-/eNOSbovþ) were obtained. Results: Western blot analysis confirmed eNOS protein expression in aorta (67.7 12.6), myocardium (49.9 5.4), lung (124.5 2.5) and skeletal muscle (87.0 25.1) of eNOS-/-/ eNOSbovþ as compared to C57Bl/6 (100%, n1⁄43-6). Aortas of eNOS-/-/eNOSbovþ showed complete restoration of endothelium-dependent relaxation to acetylcholine. The doseresponse-patterns to acetylcholine did not differ significantly (P1⁄40.562, n1⁄47-11, two-way ANOVA), and the maximal relaxations were similar in eNOS-/-/eNOSbovþ (98.3 2.14 %, n1⁄47) and C57Bl/6 mice (92.4 3.6 %, n1⁄411) while no relaxation was observed in eNOS-/(137.5 12.1, n1⁄411). Hypersensitivity to phenylephrine observed in eNOS-/mice (maximal contraction 15.2 0.7 mN, n1⁄46, P<0.0001) vs C57Bl/6 (4.6 1.1mN, n1⁄45) was blunted by endothelium-targeted reintroduction of eNOS (2.9 0.8, mN, n1⁄46). Likewise, there was a significant increase in aortic sensitivity to NO-donors S-nitroso-N-acetyl-penicillamine and diethylamine/NO in eNOS-/as compared to C57Bl/6 (n1⁄44-5, P<0.05) and this was completely abolished in eNOS-/-/eNOSbovþ (n1⁄44-5, P1⁄4 0.0278). The expression of both sGC-alpha1 and sGC-beta1 did not reveal any significant difference between eNOS-/-, eNOS-/-/eNOSbovþ and C57Bl/6 (n1⁄44, each P>0.05, ANOVA). Despite complete restoration of aortic reactivity, eNOS-/-/eNOSbovþ mice have strongly elevated systolic blood pressure (n1⁄4137.1 2.26 mmHg, n1⁄48) as compared to C57Bl/6 (118.4 3.1 mmHg, n1⁄46, P<0.05), but not to eNOS-/(135.9 2.07, n1⁄48, P1⁄40.7). Conclusions: Endothelium-specific reintroduction of functionally active eNOS in eNOSdeficient mice resulted in complete normalization of aortic reactivity but not blood pressure. These data suggest that eNOS appears to have limited effect on systemic blood pressure.