Abstract 297: Chronic Antihypertensive Effects of Sodium Nitrite in L-name-induced Hypertension in Rats
Dietary nitrite and nitrate have been recently implicated as an important source of nitric oxide with antihypertensive effects. We have previously shown acute antihypertensive effects exerted by a single oral dose of sodium nitrite (NaNO2) in renovascular hypertension. However, the possible chronic antihypertensive effects of NaNO2 have not been examined yet. We evaluated the effects of NaNO2 on L-NAME (Nω-Nitro-L-arginine methyl ester)-induced hypertension in Wistar rats.
METHODS: Rats received vehicle (tap water) or L-NAME (1g/L) in their drinking water. After two weeks of treatment, the rats received NaNO2 (15 mg/kg/day by gavage) or vehicle for 4 weeks. Systolic blood pressure (SBP) was evaluated by pletismography weekly. Plasma levels of nitrate and nitrite were assessed by Griess reaction and ozone-based chemiluminescence, respectively. Dihydroethidium (DHE) was used in aortic sections to evaluate reactive oxygen species (ROS) production by fluorescence microscopy.
Results: while NaNO2 treatment induced no changes on SBP in vehicle-treated rats (p>0.05), this treatment significantly reduced SBP in L-NAME-treated rats (192±2 mmHg in L-NAME + vehicle group versus 164±2 mmHg in L-NAME + nitrite group; P<0.05). At the end of treatment, we found lower plasma nitrite levels in L-NAME rats compared with normotensive controls (148±14 nM versus 445±97; P<0.05). NaNO2 treatment increased plasma nitrite levels in both normotensive controls and in L-NAME-treated rats (P<0.05). While no significant changes were found in plasma nitrate levels in L-NAME-treated rats when compared with controls (903±157 nM versus 995±145; p>0.05), NaNO2 treatment induced significant increases in plasma nitrate levels in both normotensive and hypertensive rats (191±13 nM and 199±17 respectively; p<0.05 when compared to the controls). When compared to the control groups, higher ROS levels were found in the aortic rings from L-NAME treated rats (4091±249 A.U. versus 5709±598 A.U.; p<0.05) but treatment did not affect this increase (p>0.05).
Conclusion: Our results show for the first time that NaNO2 has relevant chronic antihypertensive effects in L-NAME hypertension. However, was unable to reverse the oxidative stress associated with L-NAME-induced hypertension.
- © 2012 by American Heart Association, Inc.