Dietary
nitrite and
nitrate have been reported as alternative sources of
nitric oxide (NO). In this regard, we reported previously that
sodium nitrite added to
drinking water was able to exert
antihypertensive effects in an experimental model of
hypertension in a dose-dependent manner. Taking into consideration that
nitrite is continuously converted to
nitrate in the bloodstream, here we expanded our previous report and evaluate whether a single daily dose of
sodium nitrite could exert
antihypertensive effects in 2 kidney-1
clip (2K1C) hypertensive rats.
Sham-operated and 2K1C rats were treated with vehicle or
sodium nitrite (15 mg/kg/day) for 4 weeks. We evaluated the effects induced by
sodium nitrite treatment on systolic blood pressure (SBP) and NO markers such as plasma
nitrite,
nitrite +
nitrate (NOx), cGMP, and blood levels of
nitrosyl-hemoglobin. In addition, we also evaluated effects of
nitrite on oxidative stress and
antioxidant enzymes.
Dihydroethidium (DHE) was used to evaluate aortic
reactive oxygen species (ROS) production by fluorescence microscopy, and plasma levels of
thiobarbituric acid-reactive species (
TBARS) were measured in plasma samples from all experimental groups. Red blood cell
superoxide dismutase (SOD) and
catalase activity were evaluated with commercial kits.
Sodium nitrite treatment reduced SBP in 2K1C rats (P < 0.05). We found lower plasma
nitrite and NOx levels in 2K1C rats compared with normotensive controls (both P < 0.05).
Nitrite treatment restored the lower levels of
nitrite and NOx. While no change was found in the blood levels of
nitrosyl-hemoglobin (P > 0.05),
nitrite treatment increased the plasma levels of cGMP in 2K1C rats (P < 0.05). Higher plasma
TBARS levels and aortic ROS levels were found in hypertensive rats compared with controls (P < 0.05), and
nitrite blunted these alterations. Lower SOD and
catalase activities were found in 2K1C hypertensive rats compared with controls (both P < 0.05).
Nitrite treatment restored SOD activity (P < 0.05), whereas
catalase was not affected. These data suggest that even a single daily oral dose of
sodium nitrite is able to lower SBP and exert
antioxidant effects in
renovascular hypertension.