Quercetin restores plasma nitrite and nitroso species levels in renovascular hypertension

Abstract

Quercetin has antioxidants properties which may increase nitric oxide (NO) bioavailability. However, the effects of quercetin on NO status have been poorly studied. We evaluated whether quercetin improves the plasma levels of NO metabolites in two-kidney one-clip (2K1C) hypertensive rats and assessed its effect on endothelial function. Sham-operated and 2K1C rats were treated with quercetin (10 mg(-1) kg(-1) day(-1) by gavage) or vehicle for 3 weeks. Systolic blood pressure (SBP) was monitored weekly. Vascular responses to acetylcholine (Ach) and sodium nitroprusside (SNP) were assessed in hindquarter vascular bed. Plasma nitrate levels were assessed by Griess reagent and plasma nitrite and nitroso species (S, N-nitroso species) were assessed by ozone- based chemiluminescence. Aortic NADPH oxidase activity and superoxide production were evaluated. While quercetin had no effects in control normotensive rats (P > 0.05), it significantly reduced SBP in 2K1C rats (P < 0.05). At the end of treatment, plasma nitrate levels were similar in all experimental groups (P > 0.05). However, plasma nitrite and the nitroso species levels were significantly lower in 2K1C rats when compared with controls (P < 0.05). Quercetin treatment restored plasma nitrite and nitroso species levels to those found in the sham-vehicle group (P < 0.05). While quercetin treatment induced no significant changes in responses to SNP (P > 0.05), it restored the vascular responses to Ach. Quercetin significantly attenuated 2K1C-hypertension-induced increases in NADPH oxidase activity and vascular superoxide production (P < 0.05). These results suggest that the antihypertensive effects of quercetin were associated with increased NO formation and improved endothelial function, which probably result from its antioxidant effects.

Atorvastatin and sildenafil lower blood pressure and improve endothelial dysfunction, but only atorvastatin increases vascular stores of nitric oxide in hypertension

“…Time-dependent changes in nitrite concentrations in 2K1C hypertension may explain the lack of significant differences that we found with respect to nitrite concentrations. Indeed, we have consistently found lower nitrite [27,38], nitrate [38], and nitroso species [39] concentrations in 2K1C hypertensive rats compared to controls after 4 weeks of 2K1C hypertension, but not after 8 weeks of hypertension. While it might have been more interesting to determine the effects of atorvastatin and sildenafil on nitrite levels at an earlier phase of 2K1C hypertension, we wanted to avoid this phase of transition from high to low renin-angiotensin system activity [36,37].…”

Antihypertensive effects of inducible nitric oxide synthase inhibition in experimental pre‐eclampsia

“…in a Berthold FB12 single-tube luminometer at 37°C. Background signals from the aortic rings were subtracted from the β-NADPH-driven signals and the results were normalized for the dry weight and reported as lucigenin chemiluminescence/mg of dry tissue, as described previously [19]. …”

Antihypertensive and antioxidant effects of a single daily dose of sodium nitrite in a model of renovascular hypertension

“…Interestingly, we found no significant changes in plasma levels of nitrite at the end of treatment. In contrast, the plasma NOx levels (which correspond mostly to nitrate and not nitrite (Lauer et al 2001;Montenegro et al 2010) were significantly increased, thus, suggesting that exogenous sodium nitrite was virtually converted to nitrate. Interestingly, we found no increases in plasma NOx levels in sham-operated rats treated with nitrite.…”