The role of oxidative stress in renovascular hypertension.

1. There is mounting evidence that increased oxidative stress and sympathetic nerve activity play important roles in renovascular hypertension. In the present review, we focus on the importance of oxidative stress in two distinct populations of neurons involved with cardiovascular regulation: those of the rostral ventrolateral medulla (RVLM) and those of the paraventricular nucleus of the hypothalamus (PVN) in the maintenance of sympathoexcitation and hypertension in two kidney-one clip (2K1C) hypertensive rats.

Upregulation of AT1R and iNOS in the rostral ventrolateral medulla (RVLM) is essential for the sympathetic hyperactivity and hypertension in the 2K-1C Wistar rat model.

Background: We hypothesized that upregulation of angiotensin type 1 receptor (AT(1)R) and inducible nitric oxide (NO) synthase (iNOS) within the rostral ventrolateral medulla (RVLM) could contribute to two-kidney, one-clip (2K-1C) hypertension.

Methods: The experiments were performed in male Wistar rats, 6 weeks after the renal surgery. The animals were divided into control (SHAM, n = 18) and hypertensive groups (2K-1C, n = 18).

High sucrose intake in rats is associated with increased ACE2 and angiotensin-(1-7) levels in the adipose tissue.

Sucrose-fed rats, a model of metabolic syndrome, are characterized by insulin resistance, obesity, hypertension, and high plasma levels of triacylglycerols and angiotensin II (Ang II). However, whether tissue renin-angiotensin system (RAS) is altered in metabolic syndrome is unclear. To study this issue, food ad libitum and water (C) or 20% sucrose solution (SC) were given to adult male Wistar rats, for 30 days.

Oxidative stress in the sympathetic premotor neurons contributes to sympathetic activation in renovascular hypertension.

Background: Based on previous data, we hypothesized that an increase of angiotensin II (Ang II)-via the Ang II type 1 (AT-1) receptor-in the rostral ventrolateral medulla (RVLM) and the paraventricular nucleus (PVN) of the hypothalamus could activate NAD(P)H oxidase that will produce superoxides resulting in increased sympathetic activity and hypertension.

Methods: The mRNA expression of AT-1 receptors, NAD(P)H oxidase subunits (p47phox and gp91phox), and CuZnSOD were analyzed in the RVLM and PVN of male Wistar rats (Goldblatt hypertension model, 2K-1C). In addition, we administered Tempol 1 and 5 nmol into the RVLM, PVN, or systemically.

Low birth weight in response to salt restriction during pregnancy is not due to alterations in uterine-placental blood flow or the placental and peripheral renin-angiotensin system.

A number of studies conducted in humans and in animals have observed that events occurring early in life are associated with the development of diseases in adulthood. Salt overload and restriction during pregnancy and lactation are responsible for functional (hemodynamic and hormonal) and structural alterations in adult offspring. Our group observed that lower birth weight and insulin resistance in adulthood is associated with salt restriction during pregnancy.

Perinatal salt restriction: a new pathway to programming adiposity indices in adult female Wistar rats.

Low birth weight has been associated with increased obesity in adulthood. It has been shown that dietary salt restriction during intrauterine life induces low birth weight and insulin resistance in adult Wistar rats. The present study had a two-fold objective: to evaluate the effects that low salt intake during pregnancy and lactation has on the amount and distribution of adipose tissue; and to determine whether the phenotypic changes in fat mass in this model are associated with alterations in the activity of the renin-angiotensin system.

Oxidative stress contributes to renovascular hypertension.

Background: Oxidative stress is a state in which excess reactive oxygen species (ROS) overwhelm endogenous antioxidant systems. It is known that this state has been involved in the development of hypertension. On the basis of previous data, we hypothesized that overactivity of NAD(P)H oxidase-derived ROS and the lowered activity of CuZnSOD, an endogenous antioxidant within the rostral ventrolateral medulla (RVLM), could contribute to 2K-1C (two-kidney one-clip) hypertension.

Sympathetic and renin-angiotensin systems contribute to increased blood pressure in sucrose-fed rats.

Background: This study evaluated the effect of chronic sucrose feeding on hemodynamic parameters and renal sympathetic nervous activity. In addition, angiotensin I, II, and 1-7 levels were determined in plasma, heart, kidney, and the epididymal adipose tissue.

Methods: Male Wistar rats were treated for 30 days with 20% sucrose solution (n = 21) or tap water (n = 19) and food ad libitum.

Differential sympathetic and angiotensinergic responses in rats submitted to low- or high-salt diet.

The present study was designed to evaluate, in Wistar rats, the effect of high- or low-salt diet on the hemodynamic parameters and on the renal and lumbar sympathetic nerve activity. The renal gene expression of the renin angiotensin system components was also evaluated, aiming to find some correlation between salt intake, sodium homeostasis and blood pressure increase. Male Wistar rats received low (0.

Insulin resistance due to chronic salt restriction is corrected by alpha and beta blockade and by L-arginine.

Dietary salt restriction is associated with evidence of low insulin sensitivity. The current study was undertaken to investigate whether sympathetic nervous system and l-arginine-nitric oxide pathway activities are linked to insulin resistance in rats under chronic low salt intake. Male Wistar rats were fed a low (LSD) or normal (NSD) salt diet from weaning to adulthood.

High- or low-salt diet from weaning to adulthood: effect on body weight, food intake and energy balance in rats.

Objective: To get some additional insight on the mechanisms of the effect of salt intake on body weight.

Design And Methods: Rats were fed a low (LSD), normal (NSD), or high (HSD) salt diet. In a first set, body weight, tail-cuff blood pressure, fasting plasma thyroid-stimulating hormone, triiodothyronine, L-thyroxine, glucose, insulin, and angiotensin II were measured.

Central but not peripheral glucoprivation is impaired in monosodium glutamate-treated rats.

In the present study, newborn male Wistar rats were injected, subcutaneously, five times, every other day, with monosodium glutamate (MSG, 4 g/kg bw) or saline (as control, C), during the neonatal period. MSG animals developed destruction of the arcuate nuclei (ARC) with absence of NPY-immunoreactive cell bodies, which impaired both the food intake (baseline) and the 2-deoxy-D-glucose (2DG) glucoprivic feeding response. Increases in the immunoreactivity of corticotropin-releasing hormone-cell bodies in the paraventricular nuclei might have developed to compensate for the atrophy of the pituitary in MSG-treated rats.

Low salt intake modulates insulin signaling, JNK activity and IRS-1ser307 phosphorylation in rat tissues.

A severe restriction of sodium chloride intake has been associated with insulin resistance and obesity. The molecular mechanisms by which the low salt diet (LS) can induce insulin resistance have not yet been established. The c-jun N-terminal kinase (JNK) activity has been involved in the pathophysiology of obesity and induces insulin resistance by increasing inhibitory IRS-1(ser307) phosphorylation.

Perinatal salt restriction: a new pathway to programming insulin resistance and dyslipidemia in adult wistar rats.

Several studies support the hypothesis that chronic diseases in adulthood might be triggered by events that occur during fetal development. This study examined the consequences of perinatal salt intake on blood pressure (BP) and carbohydrate and lipid metabolism in adult offspring of dams on high-salt [HSD; 8% (HSD2) or 4% (HSD1)], normal-salt (NSD; 1.3%), or low-salt (LSD; 0.

Lung compliance, plasma electrolyte levels and acid-base balance are affected by scorpion envenomation in anesthetized rats under mechanical ventilation.

To determine the effects of Tityus serrulatus scorpion toxin on lung compliance and resistance, ionic equilibrium and acid-base balance over time in anesthetized and mechanically ventilated rats, we measured air flow, tracheal and esophageal pressure. Lung volume was obtained by electronic integration of airflow signal. Arterial blood samples were collected through a catheter at baseline (before) and 5, 15, 30 and 60 min after scorpion toxin injection for arterial blood gases, bicarbonate, and alkali reserve levels as well as for, sodium, potassium, magnesium, glucose, lactate, hematocrit, and osmolality analysis.

Modulation of IR/PTP1B interaction and downstream signaling in insulin sensitive tissues of MSG-rats.

PTP1B has been shown to be a negative regulator of the insulin signal transduction in insulin resistant states. Herein we investigated IR/PTP1B interaction and downstream signaling in insulin sensitive tissues of 10 and 28-week-old MSG-insulin resistant rats which represent different stages of insulin resistance. Our results demonstrated that the increase in PTP1B expression and/or association with IR in MSG animals may contribute to the impaired insulin signaling mainly in liver and muscle.

Deficit in hippocampal long-term potentiation in monosodium glutamate-treated rats.

Rats subjected to monosodium glutamate (MSG) administration during the neonatal period present chronic neuroendocrine dysfunction associated with marked cognitive deficits. Long-term potentiation (LTP) in the hippocampus provides a model suited for the study of mammalian brain plasticity and memory formation. In the present work, we used the LTP protocol to investigate the synaptic plasticity in the hippocampal CA1 area of adult rats subjected to MSG treatment during the first 10 days of life.

The rise of the plasma lipid concentration elicited by dietary sodium chloride restriction in Wistar rats is due to an impairment of the plasma triacylglycerol removal rate.

Studies in humans have indicated that dietary salt restriction raises plasma levels of total cholesterol (TC) and triacylglycerols (TAG). In order to explain the mechanisms involved, a rat experimental model was developed consisting of chronic feeding ad libitum isocaloric diets with variable sodium chloride contents. Rates of synthesis of plasma TAG were measured either as the increase of plasma TAG after blocking its removal from plasma by the intra-arterial pulse infusion of Triton-WR 1339, or as the plasma rate of incorporation of [(14)C]-oleic acid [(14)C]-TAG.

Decreased lipolysis and enhanced glycerol and glucose utilization by adipose tissue prior to development of obesity in monosodium glutamate (MSG) treated-rats.

Objective: To determine the metabolic alterations that lead to the neonatal administration of monosodium glutamate (MSG), which results in arrested growth and obesity. ANIMALS AND DESIGN: Wistar rats were injected 5 times, every other day, with 4 g of MSG/kg b.w.

High- or low-salt diet from weaning to adulthood: effect on insulin sensitivity in Wistar rats.

Because of conflicting results in the literature, further studies are needed to confirm an association between the degree of salt consumption and insulin sensitivity. The aim of this study was to measure insulin sensitivity in rats fed from weaning to adulthood with a low (LSD), normal (NSD), or high (HSD) salt diet. Body weight, carcass lipid content, blood glucose, nonesterified fatty acids, plasma insulin, plasma renin activity, and a glucose transporter (GLUT4) were measured.

Neonatal monosodium glutamate treatment alters rat intestinal muscle reactivity to some agonists.

The following study is an investigation of the changes in the contractile reactivity of visceral muscles in response to agonists and alterations in metabolic parameters after neonatal rat treatment with monosodium-L-glutamate. This treatment markedly sensitizes ileum and colon preparations to adenosine-5'-triphosphate (ATP) stimulation and also increases the colon activity to acetylcholine (p<0.05).

Effects of continuous exposure to light on behavioral dopaminergic supersensitivity.

Background: This study examines the effects of long-term continuous exposure to light on dopaminergic supersensitivity induced by repeated treatment with haloperidol in rats.

Methods: Spontaneous general activity in an open-field (SGA) and stereotyped behavior induced by apomorphine (SB-APO) or amphetamine (SB-AMP) were used as experimental parameters. Rats were allocated to four groups in each experiment: saline-treated animals kept under a 12-hour light/dark cycle (LD) or 24-hour light/light cycle (LL), and 2 mg/kg haloperidol-treated animals kept under the above cycles.

Hormonal and metabolic adaptations to fasting in monosodium glutamate-obese rats.

The effect of fasting on hormonal and metabolic variables was evaluated in normal rats and in rats with obesity induced by neonatal treatment with monosodium glutamate (MSG). The hyperinsulinemia of the fed obese rats was reversed by fasting. Plasma corticosterone was also high in the fed obese and decreased to levels similar to fed controls, while it increased in the latter group during fasting.

Ligation of the left renal vein in epm1-Wistar rats: functional and morphologic alterations in the kidneys, testes and suprarenal glands.

Objective: The ligation of the left renal vein (LLVR) in man is a controversial procedure in view of the risks of lesion to the renal parenchyma. With the objective of studying the morphologic and functional alterations caused by these lesions, we conducted experimental research with rats.

Material And Methods: 64 male adult EPM1-WISTAR rats were used, divided into 8 groups-4 for LLRV and four for control.

Monosodium glutamate (MSG)-obese rats develop glucose intolerance and insulin resistance to peripheral glucose uptake.

Different levels of insulin sensitivity have been described in several animal models of obesity as well as in humans. Monosodium glutamate (MSG)-obese mice were considered not to be insulin resistant from data obtained in oral glucose tolerance tests. To reevaluate insulin resistance by the intravenous glucose tolerance test (IVGTT) and by the clamp technique, newborn male Wistar rats (N = 20) were injected 5 times, every other day, with 4 g/kg MSG (N = 10) or saline (control; N = 10) during the first 10 days of age.