title: Dietary doses of nitrite restore circulating nitric oxide level and improve renal injury in L-NAME-induced hypertensive rats.
abstract: We have reported that pharmacological doses of oral nitrite increase circulating nitric oxide (NO) and exert hypotensive effects in Nomega-nitro-L-arginine methyl ester (L-NAME)-induced hypertensive rats. In this study, we examined the effect of a chronic dietary dose of nitrite on the hypertension and renal damage induced by chronic L-NAME administration in rats. The animals were administered tap water containing L-NAME (1 g/l) or L-NAME + nitrite (low dose: 0.1 mg/l, medium dose: 1 mg/l, high dose: 10 mg/l) for 8 wk. We evaluated blood NO levels as hemoglobin-NO adducts (iron-nitrosyl-hemoglobin), using an electron paramagnetic resonance method. Chronic administration of L-NAME for 8 wk induced hypertension and renal injury and reduced the blood iron-nitrosyl-hemoglobin level (control 38.8 +/- 8.9 vs. L-NAME 6.0 +/- 3.1 arbitrary units). Coadministration of a low dose of nitrite with L-NAME did not change the reduced iron-nitrosyl-hemoglobin signal and did not improve the L-NAME-induced renal injury. The blood iron-nitrosyl-hemoglobin signals of the medium dose and high dose of nitrite were significantly higher than that of L-NAME alone. Chronic administration of a medium dose of nitrite attenuated L-NAME-induced renal histological changes and proteinuria. A high dose of nitrite also attenuated L-NAME-induced renal injury. These findings suggest that dietary doses of nitrite that protect the kidney are associated with significant increase in iron-nitrosyl-hemoglobin levels. We conclude that dietary nitrite-derived NO generation may serve as a backup system when the nitric oxide synthase/L-arginine-dependent NO generation system is compromised.
authors.affiliation: Department of Pharmacology, Institute of Health Biosciences, University of Tokushima Graduate School, 3-18-15 Kuramoto, Tokushima-city, Tokushima 770-8503, Japan.
authors.forename: Yasuhisa
authors.initials: Y
authors.lastname: Kanematsu
authors.forename: Kunihisa
authors.initials: K
authors.lastname: Yamaguchi
authors.forename: Hideki
authors.initials: H
authors.lastname: Ohnishi
authors.forename: Yuki
authors.initials: Y
authors.lastname: Motobayashi
authors.forename: Keisuke
authors.initials: K
authors.lastname: Ishizawa
authors.forename: Yuki
authors.initials: Y
authors.lastname: Izawa
authors.forename: Kazuyoshi
authors.initials: K
authors.lastname: Kawazoe
authors.forename: Shuji
authors.initials: S
authors.lastname: Kondo
authors.forename: Shoji
authors.initials: S
authors.lastname: Kagami
authors.forename: Shuhei
authors.initials: S
authors.lastname: Tomita
authors.forename: Koichiro
authors.initials: K
authors.lastname: Tsuchiya
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Tamaki