Interactions between nitric oxide and renal nerves in the excretion of a saline load in obese Zucker rats.

The present study investigated the potential role of nitric oxide (NO) and its interaction with renal sympathetic nerves in modulating the excretory responses to an acute saline volume expansion (VE), of 10% of body weight, in the innervated and denervated kidneys of both lean and obese Zucker rats. This was done using the NO synthase inhibitors N(G)-nitro-L-arginine methyl ester (L-NAME), 7-nitroindazole and aminoguanidine. In lean rats, cumulative urinary sodium excretion (cuU(Na)V) after 40 min of VE in the innervated kidney was enhanced by 48% in L-NAME-treated rats compared with that in untreated rats, but this was not the case for the denervated kidney.

Contribution of endothelial nitric oxide synthase in the blunted renal responses to volume expansion in diabetic rats.

The renal excretory responses to volume expansion (VE), by 10 % body wt, were determined in groups of anaesthetised streptozotocin-induced diabetic rats with one denervated and one innervated kidney in the presence and absence of nitric oxide synthase (NOS) inhibitors. VE in diabetic rats increased (P < 0.001) cumulative urine sodium excretion (CuU(Na)V) to 104 +/- 9 and 69 +/- 6 micromol min(-1) (g kidney wt)(-1) in the denervated and in the innervated kidneys, respectively, which were both less (P < 0.

Role of nitric oxide and renal nerves in the renal responses to acute volume expansion in anaesthetized rats.

An investigation was undertaken into the potential role of nitric oxide (NO) and its interaction with renal sympathetic nerves in mediating renal responses to acute saline volume expansion (VE). Groups of anaesthetized Wistar rats with innervated and denervated kidneys were subjected to VE, 0.25 % body wt min-1 for 40 min, in the presence and absence of nitric oxide synthase (NOS) inhibitors, NG-nitro-L-arginine-methyl-ester (L-NAME, non-selective), aminoguanidine (AG, relatively selective for inducible NOS (iNOS)), and 7-nitroindazole (7-NI, relatively selective for neuronal NOS (nNOS)).

Role of brain angiotensin II on somatosensory-induced antinatriuresis in hypertensive rats.

The aim of this investigation was to compare the contribution of brain angiotensin II in mediating the transmission of a somatosensory stimulus within the brain to generate a renal sympathetic nerve-dependent antidiuresis and antinatriuresis in normotensive Wistar rats and stroke-prone spontaneously hypertensive rats (SHRSP). In anesthetized Wistar rats, stimulation of somatosensory receptors by subcutaneous capsaicin increased blood pressure by 9%, had no effect on renal hemodynamics, but decreased urinary flow and sodium excretion by 30% to 40%. These antidiuretic and antinatriuretic, but not blood pressure, responses were absent after intracerebroventricular losartan administration to block angiotensin II type 1 receptors.

The role of haem oxygenase in renal vascular reactivity in normotensive and hypertensive rats.

Objective: To evaluate the contribution of the haem oxygenase-carbon monoxide (CO) system to renal vascular tone in normotensive Wistar rats and in the stroke-prone spontaneously hypertensive rats (SHR-SPs).

Methods: An isolated perfused rat kidney preparation was used in which perfusion pressure/phenylephrine dose-vasoconstrictor responses were generated. Haemin was given 24 h previously, to induce haem oxygenase-1 (HO-1), and L-NAME (N-omega-nitro-L-arginine methyl ester) was given to block nitric oxide (NO) production.

Acute renal failure in 2K2C Goldblatt hypertensive rats during antihypertensive therapy: comparison of an angiotensin AT1 receptor antagonist and clonidine analogues.

1. This study compared the effect of a non-peptide angiotensin II receptor antagonist and a series of clonidine analogues on blood pressure and renal function in a two-kidney two-clip Goldblatt rat model of hypertension subjected to 2 weeks of dietary sodium deprivation. 2.

Early effects of renal denervation in the anaesthetised rat: natriuresis and increased cortical blood flow.

A novel method of renal denervation was developed based on electro-coagulation of tissue containing most of the sympathetic fibres travelling towards the kidney. Kidney tissue noradrenaline was decreased to 4.7 % of the content measured in the contralateral innervated kidney when studied 3 days postdenervation.

beta(2)-adrenoceptor agonist suppresses renal tumour necrosis factor and enhances interleukin-6 gene expression induced by endotoxin.

Background: beta(2)-Adrenoceptor activation regulates tumour necrosis factor (TNF)-alpha and interleukin-6 (IL-6) production in cultured renal cells. However, it remains uncertain whether, in vivo, the administration of beta(2)-adrenoceptor agonists regulate renal TNF-alpha and IL-6 mRNA following lipopolysaccharide (LPS) stimulation to cause endotoxaemia. This study was performed in order to evaluate the effect of beta(2)-adrenoceptor agonist on renal TNF-alpha and IL-6 production.

The extralist-feature effect: evidence against item matching in short-term recognition memory.

The authors varied the similarity between negative probes and study items in a short-term item-recognition task. Current models treat similarity as a function of the number of occurrences of the probe's features in the study set, a factor that is often confounded with the number of the probe's features occurring in the study set. Unconfounded comparisons showed that performance reflected only the latter factor, with response time a linear function of the number of probe features in the study set.

Beta2-adrenoceptor agonist suppresses tumour necrosis factor production in rat mesangial cells.

This study aimed to investigate the time-course of the effect of beta2-adrenoceptor stimulation with terbutaline on lipopolysaccharide (LPS)-induced tumour necrosis factor(TNF)-alpha production in rat mesangial cells. Cells were cultured from 0-24 h in the presence of LPS (1 microg/ml) and/or terbutaline (10(-7)-10(-8) mol/l). After 1 h of incubation, terbutaline inhibited TNF-alpha protein release as well as transcription and translation of TNF-alpha and mitogen activated protein kinase (MAPK, p42/p44) activity.

Role of brain angiotensin II in the somatosensory induced antinatriuresis in the anaesthetized rat.

1. The present study set out to explore the importance of angiotensin (Ang)II in the brain in allowing the somatosensory system to cause a reflex renal nerve-mediated reduction in renal sodium and water excretion. 2.

Investigating the relaxation rate, following diazo-2 photolysis, of a skinned trabecular preparation from guinea-pig hypertrophied left ventricle.

Cardiac hypertrophy in the guinea-pig is not accompanied by a large shift in the expression of the predominant isoform of myosin in the left ventricle; however, in this species, thin filament proteins do change. We examined the relaxation, following laser flash photolysis of the photolabile caged Ca2+ chelator diazo-2, of a skinned trabecular preparation from the left ventricle of guinea-pigs that had undergone abdominal aortic banding. Sham-operated animals were used as controls; no guinea-pigs showed any signs of heart failure.

Role of erythropoietin and nitric oxide in modulating the tone of human renal interlobular and subcutaneous arteries from uraemic subjects.

This study investigated potential reasons why erythropoietin (EPO) given therapeutically to patients with renal failure may increase peripheral, but not renal, vascular resistance. This was done by comparing the effects of EPO on resting tension in normal renal interlobular and subcutaneous vessels from uraemic patients. In human subcutaneous arteries from uraemic subjects, noradrenaline- and KCl-induced vasoconstrictions were enhanced when nitric oxide (NO) production was blocked with N(G)-nitro-L-arginine methyl ester (L-NAME), but were unaffected by EPO, while acetylcholine- and bradykinin-induced concentration-dependent relaxations were markedly attenuated by L-NAME, but not by EPO.

Effect of beta(2)-adrenoceptor activation and angiotensin II on tumour necrosis factor and interleukin 6 gene transcription in the rat renal resident macrophage cells.

This study aimed to examine whether lipopolysaccharide (LPS)-induced increase in tumour necrosis factor alpha (TNF-alpha) and interleukin 6 (IL-6) gene transcription was regulated by beta-adrenoceptor activation and whether TNF-alpha and IL-6 gene transcription was regulated by angiotensin II in rat renal resident macrophage cells. The cells were transfected with a fusion gene with the 5'-flanking region of rat TNF-alpha or IL-6 genes linked to a luciferase coding sequence as a reporter. The stimulatory effect of LPS on TNF-alpha transcription was suppressed by isoproterenol (10(-8)-10(-5)M) in a dose-dependent manner, whereas IL-6 transcription was only decreased by the high concentration (10(-5)M) of isoproterenol.

Effect of renal perfusion pressure on renal function, renin release and renin and angiotensinogen gene expression in rats.

1. A study was undertaken to examine the influence of acute renal perfusion pressure (RPP) reduction on renin release, renal renin and angiotensinogen gene expression and the role played by angiotensin II in these responses. 2.

Influence of endothelins and sarafotoxin 6c and L-NAME on renal vasoconstriction in the anaesthetized rat.

1. An investigation was performed in pentobarbitone anaesthetized rats to compare the renal vasoconstrictor actions of endothelin-1 (ET-1), endothelin-3 (ET-3) and sarafotoxin 6c and their dependency on NO production. 2.

Nitric oxide and renal nerve-mediated proximal tubular reabsorption in normotensive and hypertensive rats.

In Inactin-anesthetized Wistar rats with an intact renal innervation, intratubular nitro-L-arginine methyl ester (L-NAME, 10(-4) M) increased proximal fluid uptake (J(va), at 2.47 +/- 0.61 x 10(-4) mm(3).

The influence of erythropoietin on the vascular responses of rat resistance arteries.

This study examined the effect of erythropoietin (EPO) on resting tension and on the responses of rat mesenteric and renal arcuate arteries in vitro to a number of agonists as a possible cause of its blood pressure elevating properties when used therapeutically. Noradrenaline and potassium chloride induced concentration-dependent vasoconstrictions in both vessel types but the basal tension, maximum tension, and the -log concentration producing half-maximal response (pEC50) were altered in the presence of 0.1 or 20 U ml-1 EPO.

The influence of allopurinol on kidney haemodynamic and excretory responses to renal ischaemia in anaesthetized rats.

1. This study examined the impact of allopurinol on the renal functional responses to a 30 min period of ischaemia in anaesthetized rats. 2.

Relationship between erythropoietin and nitric oxide in the contraction of rat renal arcuate arteries and human umbilical vein endothelial cells.

We have investigated the effects of recombinant human erythropoietin (EPO) on the responses of rat renal arcuate arteries to dopamine, noradrenaline and acetylcholine and on the release of NO from human umbilical vein endothelial cells (HUVEC) in culture. Noradrenaline induced a concentration-dependent constriction and acetylcholine a concentration-dependent relaxation of the vessels. The effects of dopamine were concentration-dependent, leading to relaxation of the vessels at low concentrations and contraction of the vessels at high concentrations.

Modulation of interleukin-6 by beta2-adrenoceptor in endotoxin-stimulated renal macrophage cells.

Background: Activation of the cAMP signaling pathway by means of beta2-adrenoceptor agonists has been shown to up-regulate interleukin-6 (IL-6) gene expression and to stimulate IL-6 production in macrophage cells. However, whether beta2-adrenoceptor activation can also modify the rate of IL-6 production in macrophage cells activated by the bacterial endotoxins has not yet been determined. Using renal resident macrophage cells treated with endotoxin, lipopolysaccharide (LPS), and beta2-adrenoceptor agonist, terbutaline, we investigated the role of cAMP pathway, tumor necrosis factor (TNF)-alpha and mitogen-activated protein kinase (MAPK) pathway (p42/p44) in regulating IL-6 production.

The effect of nitrendipine on renal haemodynamics and tubular reabsorption and its neural control in anaesthetised rats with chronic renal failure.

This study examined the influence of a calcium channel antagonist, nitrendipine, on blood pressure and kidney function in a rat model of chronic renal failure. Additionally, the effects of low frequency renal nerve stimulation were studied in the presence and absence of nitrendipine. Male Wistar rats were fed a diet high in adenine for 4 weeks and then acutely anaesthetised and prepared for renal functional measurements.

Effect of acute saline volume loading on renal sympathetic nerve activity in anaesthetised fructose-fed and fat-fed rats.

Experiments were conducted to investigate the effects of activation of cardiopulmonary vagal afferent nerve endings by acute saline volume expansion on sympathetic efferent renal nerve activity in anaesthetised fat-fed and fructose-fed Wistar rats. Four weeks of fat feeding caused obesity in the Wistar rats which was associated with a mild elevation in blood pressure (118 +/- 4 mmHg vs. 105 +/- 1 mmHg in the lean control rats, P < 0.

Chaotic characteristics of renal nerve peak interval sequence in normotensive and hypertensive rats.

1. The use of non-linear dynamic analysis for the measurement of control processes in low-dimensional signals, for example, blood pressure and heart rate variability, are well established and accepted. However, the application of these analytical techniques to a high-dimensional signal, such as renal sympathetic nerve activity (RSNA), has not been validated.

Effect of pH, phosphate, and ADP on relaxation of myocardium after photolysis of diazo 2.

The aim of this study was to examine the effect of the metabolites H+, ADP, and Pi on the rate of cardiac relaxation. We used guinea pig right ventricular trabeculae that had been chemically skinned, allowing the myofilaments to be studied in isolation. Laser-flash photolysis of the caged Ca2+ chelator diazo 2, causing a rapid fall in intracellular Ca2+, enabled investigation of relaxation independently of the rate of Ca2+ diffusion.