Reduced renal responses to nitric oxide synthase inhibition in mice lacking the gene for gp91^phoxsubunit of NAD(P)H oxidase

Abstract

Ϫ activity in the kidney, responses to administration of the NO synthase inhibitor nitro-L-arginine methyl ester (L-NAME; 200 g ⅐ min Ϫ1 ⅐ kg body wt Ϫ1 ) were assessed in knockout mice the lacking NAD(P)H oxidase subunit gp91 phox (KO; n ϭ 10) and in wild-type (WT; n ϭ 10) mice. Renal blood flow (RBF) and glomerular filtration rate (GFR) were determined by PAH and inulin clearances, respectively. Baseline RBF was higher in KO compared with WT mice (5.8 Ϯ 0.5 vs. 4.5 Ϯ 0.3 ml ⅐ min Ϫ1 ⅐ g Ϫ1 ; P Ͻ 0.04) without significant differences in GFR (0.62 Ϯ 0.04 vs. 0.73 Ϯ 0.05 ml ⅐ min Ϫ1 ⅐ g Ϫ1 ) and in mean arterial pressure (MAP; 91 Ϯ 6 vs. 88 Ϯ 4 mmHg). L-NAME infusion for 60 min caused similar increases in MAP (114 Ϯ 6 vs. 113 Ϯ 3 mmHg) in both groups but resulted in a lesser degree of reduction in RBF in KO compared with WT mice (Ϫ7 Ϯ 3 vs. Ϫ17 Ϯ 3%; P Ͻ 0.02), although GFR remained unchanged in both groups. The natriuretic response to systemic L-NAME infusion was attenuated in KO compared with WT mice (⌬: 3.1 Ϯ 0.7 vs. 5.2 Ϯ 0.6 mol ⅐ min Ϫ1 ⅐ g Ϫ1 ). L-NAME increased urinary 8-isoprostane excretion rate in WT (5.9 Ϯ 1 to 7.7 Ϯ 1 pg ⅐ min Ϫ1 ⅐ g Ϫ1 ; P Ͻ 0.02) but not in KO mice (5.6 Ϯ 1 to 4.9 Ϯ 0.3 pg ⅐ min Ϫ1 ⅐ g Ϫ1 ). In contrast, responses to another vasoconstrictor, norepinephrine, were similar in both strains of mice. These data indicate that activation of NAD(P)H oxidase results in the enhancement of O 2 Ϫ activity that influences renal hemodynamics and excretory function in the condition of NO deficiency. superoxide; oxidative stress; renal blood flow; sodium excretion; 8-isoprostane excretion CURRENT LITERATURE REVEALS an increasing recognition that the interaction between nitric oxide (NO) and superoxide (O 2 Ϫ ) plays an important role in the physiology as well as in the pathophysiology of kidney function and in hypertension (8,19,(23)(24)(25)42). Most of the evidence suggests that there is a balance between the production of NO and O 2 Ϫ that regulates the body function by opposing each other's action. It was demonstrated in vitro that O 2 Ϫ production was increased during NO inhibition in an isolated aortic strip (11). Enhancement of O 2 Ϫ activity by inhibiting SOD enzymes has been shown to decrease renal blood flow (RBF) and sodium excretion (U Na V; Refs. 8,19,20,24,26), and these responses to SOD inhibition were markedly enhanced during inhibition of the NO synthase (NOS) enzyme (20,24,25

Involvement of tumor necrosis factor-α in natriuretic response to systemic infusion of nitric oxide synthase inhibitor in anesthetized mice

“…These findings generally resemble those with acute systemic infusion of NOS inhibitors, as mentioned earlier (3,16,18). Previously, it had been demonstrated that a high-salt (8%) diet induced increases in the production of various inflammatory cytokines including TNF-␣ in Dahl saltsensitive rats (41).…”

“…A blockade of NO synthesis by L-NAME administration in experimental animals leads to development of an oxidative stress condition, as indicated by an associated increase in U Iso V in many previous experiments in vivo (16,22,31) and an increase in vascular O 2 Ϫ production in vitro (38). It was also suggested that the production of inflammatory molecules such as TNF-␣ may be induced by the condition of oxidative stress (34,44).…”

“…An infusion of L-NAME (0.2 g · g Ϫ1 · min Ϫ1 , Sigma), dissolved in isotonic saline containing 1% albumin, 7.5% inulin, and 1.5% PAH, was then initiated and continued until the end of the experiment. The dose of L-NAME used in this study was selected on the basis of a previous study with L-NAME from our laboratory (16). Twenty-five minutes after the initiation of L-NAME infusion (stabilization period), another two 30-min urine clearance collections were made (L-NAME treatment period).…”

“…On the other hand, acute systemic administration of NOS inhibitors in rodents has been reported to cause marked diuresis and natriuresis in many studies although it reduces RBF or glomerular filtration (3,16,18). The exact mechanism of these diuretic and natriuretic responses to systemic infusion of NOS inhibitors still remains unclear.…”

Reactive oxygen species and vascular biology: implications in human hypertension

“…134,135 OXIDATIVE STRESS AND HUMAN HYPERTENSION Almost all experimental models of hypertension show some form of oxidative excess including genetic forms (spontaneously hypertensive rats, stroke-prone spontaneously hypertensive rats), surgically induced (2K1C, aortic banding), endocrine-induced (Ang II, aldosterone, deoxycorticosterone acetate) and diet-induced hypertension (salt, fat). [21][22][23][136][137][138] Sources of ROS in experimental models include Noxes (Nox1, Nox2 and Nox4), xanthine oxidase, uncoupled nitric oxide synthase and mitochondrial oxidases. Mice deficient in ROSgenerating enzymes have lower blood pressure compared with wild-type counterparts, and Ang II infusion fails to induce hypertension in these mice.…”