Effects of dexmedetomidine on kidney and brain tissue microcirculation and histology in ovine cardiopulmonary bypass: a randomised controlled trial.

Cardiac surgery requiring cardiopulmonary bypass is associated with postoperative acute kidney injury and neurocognitive disorders, including delirium. Intra-operative inflammation and/or impaired tissue perfusion/oxygenation are thought to be contributors to these outcomes. It has been hypothesised that these problems may be ameliorated by the highly selective α2 -agonist, dexmedetomidine. We tested the effects of dexmedetomidine on renal and cerebral microcirculatory tissue perfusion, oxygenation and histology in a clinically relevant ovine model. Sixteen sheep were studied while conscious, after induction of anaesthesia and during 2 h of cardiopulmonary bypass. Eight sheep were allocated randomly to receive an intravenous infusion of dexmedetomidine (0.4-0.8 µg.kg-1 .h-1 ) from induction of anaesthesia to the end of cardiopulmonary bypass, and eight to receive an equivalent volume of matched placebo (0.9% sodium chloride). Commencement of cardiopulmonary bypass decreased renal medullary tissue oxygenation in the placebo group (mean (95%CI) 5.96 (4.24-7.23) to 1.56 (0.84-2.09) kPa, p = 0.001), with similar hypoxic levels observed in the dexmedetomidine group (6.33 (5.33-7.07) to 1.51 (0.33-2.39) kPa, p = 0.002). While no differences in kidney function (i.e. reduced creatinine clearance) were evident, a greater incidence of histological renal tubular injury was observed in sheep receiving dexmedetomidine (7/8 sheep) compared with placebo (2/8 sheep), p = 0.041. Graded on a semi-quantitative scale (0-3), median (IQR [range]) severity of histological renal tubular injury was higher in the dexmedetomidine group compared with placebo (1.5 (1-2 [0-3]) vs. 0 (0-0.3 [0-1]) respectively, p = 0.013). There was no difference in cerebral tissue microglial activation (neuroinflammation) between the groups. Dexmedetomidine did not reduce renal medullary hypoxia or cerebral neuroinflammation in sheep undergoing cardiopulmonary bypass.

Renal hypoxia in kidney disease: Cause or consequence?

Tissue hypoxia has been proposed as an important factor in the pathophysiology of both chronic kidney disease (CKD) and acute kidney injury (AKI), initiating and propagating a vicious cycle of tubular injury, vascular rarefaction, and fibrosis and thus exacerbation of hypoxia. Here, we critically evaluate this proposition by systematically reviewing the literature relevant to the following six questions: (i) Is kidney disease always associated with tissue hypoxia? (ii) Does tissue hypoxia drive signalling cascades that lead to tissue damage and dysfunction? (iii) Does tissue hypoxia per se lead to kidney disease? (iv) Does tissue hypoxia precede pathology? (v) Does tissue hypoxia colocalize with pathology? (vi) Does prevention of tissue hypoxia prevent kidney disease? We conclude that tissue hypoxia is a common feature of both AKI and CKD. Furthermore, at least under in vitro conditions, renal tissue hypoxia drives signalling cascades that lead to tissue damage and dysfunction. Tissue hypoxia itself can lead to renal pathology, independent of other known risk factors for kidney disease. There is also some evidence that tissue hypoxia precedes renal pathology, at least in some forms of kidney disease. However, we have made relatively little progress in determining the spatial relationships between tissue hypoxia and pathological processes (i.e. colocalization) or whether therapies targeted to reduce tissue hypoxia can prevent or delay the progression of renal disease. Thus, the hypothesis that tissue hypoxia is a "common pathway" to both AKI and CKD still remains to be adequately tested.

Renal haemodynamics and oxygenation during and after cardiac surgery and cardiopulmonary bypass.

Acute kidney injury (AKI) is a common complication following cardiac surgery performed on cardiopulmonary bypass (CPB) and has important implications for prognosis. The aetiology of cardiac surgery-associated AKI is complex, but renal hypoxia, particularly in the medulla, is thought to play at least some role. There is strong evidence from studies in experimental animals, clinical observations and computational models that medullary ischaemia and hypoxia occur during CPB. There are no validated methods to monitor or improve renal oxygenation during CPB, and thus possibly decrease the risk of AKI. Attempts to reduce the incidence of AKI by early transfusion to ameliorate intra-operative anaemia, refinement of protocols for cooling and rewarming on bypass, optimization of pump flow and arterial pressure, or the use of pulsatile flow, have not been successful to date. This may in part reflect the complexity of renal oxygenation, which may limit the effectiveness of individual interventions. We propose a multi-disciplinary pathway for translation comprising three components. Firstly, large-animal models of CPB to continuously monitor both whole kidney and regional kidney perfusion and oxygenation. Secondly, computational models to obtain information that can be used to interpret the data and develop rational interventions. Thirdly, clinically feasible non-invasive methods to continuously monitor renal oxygenation in the operating theatre and to identify patients at risk of AKI. In this review, we outline the recent progress on each of these fronts.

Factors associated with awareness, treatment and control of hypertension in a disadvantaged rural Indian population.

The aim of this study was to identify factors associated with awareness, treatment and control of hypertension in a rural setting in India. Following screening of the population, all individuals with hypertension (blood pressure (BP) ⩾140/90 mm Hg or taking antihypertensive medications) were invited to participate in this study. We measured BP, height, weight, skinfolds, waist and hip circumference, and administered a questionnaire to obtain information regarding socioeconomic and behavioural characteristics. Multivariable logistic regression was used to determine factors associated with awareness, treatment and control of hypertension. We recruited 277 individuals with hypertension. Awareness (43%), treatment (33%) and control (27%) of hypertension were poor. Greater distance to health services (odds ratio (OR) 0.56 (95% confidence interval (CI)) 0.32-0.98) was associated with poor awareness of hypertension while having had BP measured within the previous year (OR 4.72, 95% CI 2.71-8.22), older age and greater per cent body fat were associated with better awareness. Factors associated with treatment of hypertension were having had BP measured within the previous year (OR 6.18, 95% CI 3.23-11.82), age ⩾65 years, physical inactivity and greater per cent body fat. The only factor associated with control of hypertension was greater per cent body fat (OR 1.05, 95% CI 1.01-1.11). Improving geographic access and utilisation of health services should improve awareness and treatment of hypertension in this rural population. Further research is necessary to determine drivers of control.

Normotension, hypertension and body fluid regulation: brain and kidney.

The fraction of hypertensive patients with essential hypertension (EH) is decreasing as the knowledge of mechanisms of secondary hypertension increases, but in most new cases of hypertension the pathophysiology remains unknown. Separate neurocentric and renocentric concepts of aetiology have prevailed without much interaction. In this regard, several questions regarding the relationships between body fluid and blood pressure regulation are pertinent. Are all forms of EH associated with sympathetic overdrive or a shift in the pressure-natriuresis curve? Is body fluid homoeostasis normally driven by the influence of arterial blood pressure directly on the kidney? Does plasma renin activity, driven by renal nerve activity and renal arterial pressure, provide a key to stratification of EH? Our review indicates that (i) a narrow definition of EH is useful; (ii) in EH, indices of cardiovascular sympathetic activity are elevated in about 50% of cases; (iii) in EH as in normal conditions, mediators other than arterial blood pressure are the major determinants of renal sodium excretion; (iv) chronic hypertension is always associated with a shift in the pressure-natriuresis curve, but this may be an epiphenomenon; (v) plasma renin levels are useful in the analysis of EH only after metabolic standardization and then determination of the renin function line (plasma renin as a function of sodium intake); and (vi) angiotensin II-mediated hypertension is not a model of EH. Recent studies of baroreceptors and renal nerves as well as sodium intake and renin secretion help bridge the gap between the neurocentric and renocentric concepts.

Augmented endothelial-specific L-arginine transport prevents obesity-induced hypertension.

AIM: Hypertension is a major clinical complication of obesity. Our previous studies show that abnormal uptake of the nitric oxide precursor L-arginine, via the cationic amino acid transporter-1 (CAT1), contributes to endothelial dysfunction in cardiovascular disease. In this study, we tested the hypothesis that abnormal L-arginine transport may be a key mediator of obesity-induced hypertension. METHODS: Mean arterial pressure (MAP) was monitored by telemetry in conscious wild-type (WT; n = 13) mice, and transgenic mice with endothelial-specific overexpression of CAT1 (CAT+; n = 14) fed a normal or a high fat diet for 20 weeks. Renal angiotensin II (Ang II), CAT1 mRNA and plasma nitrate/nitrite levels were then quantified. In conjunction, plasma nitrate/nitrite levels were assessed in obese normotensive (n = 15) and obese hypertensive subjects (n = 15). RESULTS: Both genotypes of mice developed obesity when fed a high fat diet (P ≤ 0.002). Fat fed WT mice had 13% greater MAP and 78% greater renal Ang II content, 42% lesser renal CAT1 mRNA levels and 42% lesser plasma nitrate/nitrite levels, than WT mice fed a normal fat diet (P ≤ 0.02). In contrast, none of these variables were significantly altered by high fat feeding in CAT+ mice (P ≥ 0.36). Plasma nitrate/nitrite levels were 17% less in obese hypertensives compared with obese normotensives (P = 0.02). CONCLUSION: Collectively, these data indicate that obesity-induced down-regulation of CAT1 expression and subsequent reduced bioavailability of nitric oxide may contribute to the development of obesity-induced hypertension.

Endothelial cationic amino acid transporter-1 overexpression can prevent oxidative stress and increases in arterial pressure in response to superoxide dismutase inhibition in mice.

AIM: Oxidative stress may play an important role in the pathogenesis of hypertension. The aim of our study is to examine whether increased expression of the predominant endothelial l-arginine transporter, cationic amino acid transporter-1 (CAT1), can prevent oxidative stress-induced hypertension. METHODS: Wild-type mice (WT; n = 9) and endothelial CAT1 overexpressing (CAT+) mice (n = 6) had telemetry probes implanted for the measurement of mean arterial pressure (MAP), heart rate (HR) and locomotor activity. Minipumps were implanted for infusion of the superoxide dismutase inhibitor diethyldithiocarbamic acid (DETCA; 30 mg kg(-1) day(-1) ; 14 days) or its saline vehicle. Baseline levels of MAP, HR and locomotor activity were determined before and during chronic DETCA administration. Mice were then killed, and their plasma and kidneys collected for analysis of F2 -isoprostane levels. RESULTS: Basal MAP was less in CAT+ (92 ± 2 mmHg; n = 6) than in WT (98 ± 2 mmHg; n = 9; P < 0.001). During DETCA infusion, MAP was increased in WT (by 4.2 ± 0.5%; P < 0.001) but not in CAT+, when compared to appropriate controls (PDETCA*genotype = 0.006). DETCA infusion increased total plasma F2 -isoprostane levels (by 67 ± 11%; P = 0.05) in WT but not in CAT+. Total renal F2 -isoprostane levels were greater during DETCA infusion in WT (by 72%; P < 0.001), but not in CAT+, compared to appropriate controls. CONCLUSION: Augmented endothelial l-arginine transport attenuated the prohypertensive effects of systemic and renal oxidative stress, suggesting that manipulation of endothelial CAT1 may provide a new therapeutic approach for the treatment of cardiovascular disease associated with oxidative stress.

In-depth plasma-wave heating of dense plasma irradiated by short laser pulses.

We investigate the mechanism by which relativistic electron bunches created at the surface of a target irradiated by a very short and intense laser pulse transfer energy to the deeper parts of the target. In existing theories, the dominant heating mechanism is that of resistive heating by the neutralizing return current. In addition to this, we find that large amplitude plasma waves are induced in the plasma in the wake of relativistic electron bunches. The subsequent collisional damping of these waves represents a source of heating that can exceed the resistive heating rate. As a result, solid targets heat significantly faster than has been previously considered. A new hybrid model, capable of reproducing these results, is described.

Symmetry of spherically converging shock waves through reflection, relating to the shock ignition fusion energy scheme.

We examine the properties of perturbed spherically imploding shock waves in an ideal fluid through the collapse, bounce, and development into an outgoing shock wave. We find broad conservation of the size and shape of ingoing and outgoing perturbations when viewed at the same radius. The outgoing shock recovers the velocity of the unperturbed shock outside the strongly distorted core. The results are presented in the context of the robustness of the shock ignition approach to inertial fusion energy.

First Report of Spot Form Net Blotch Caused by Pyrenophora teres f. maculata on Barley in the Mon-Dak Area of the United States.

Pyrenophora teres Drechs. causes net blotch of barley, a common foliar disease in cultivation zones around the world. The disease occurs in two forms, namely a net form net blotch (NFNB) caused by P. teres f. teres and a spot form net blotch (SFNB) caused by P. teres f. maculata. As in other parts of the northern Great Plains, in the Mon-Dak area (western North Dakota and eastern Montana), NFNB is prevalent. SFNB was first reported in western Montana in 1983 (1) and more recently in eastern North Dakota in 2010 (3) but not in the Mon-Dak area. In the summer of 2011, unusual spot lesions that were surrounded by necrosis or chlorosis were observed on different barley cultivars in fields at Williston, ND, Nesson Valley, ND, and Sidney, MT areas. Diseased leaves from various barley cvs. from the three locations were transferred to water agar and incubated at room temperature for 24 h to induce sporulation. Morphological examination of conidia (45 to 169 × 15 to 21 µm) did not show significant differences from a known isolate of P. teres f. teres 0-1 (provided by Tim Friesen, ARS, Fargo, ND). For pathogenicity testing, six 14-day-old plants of barley cv. Tradition were sprayed until runoff with a 2,000 spore/ml suspension of two isolates from each location and the control P. teres f. maculata isolate DEN2.6 (provided by Tim Friesen). Plants were incubated first in a lighted humidity chamber for 24 h and then in a greenhouse for 7 days at 21°C. Regardless of inoculum source, spot lesions surrounded by necrosis or chlorosis, typical of SFNB, appeared on the inoculated leaves within 7 days. Fungi isolated from symptomatic leaves were identified as P. teres and the morphology of the conidia was undistinguishable from those of P. teres f. teres. All control plants which were sprayed with sterile distilled water were symptomless. The pathogenicity test was repeated. Rapid PCR detection and amplicon sequencing (2) of the internal transcribed spacer (ITS) region of ribosomal genes was performed on field and pathogenicity test leaf lesion samples to confirm the presence of P. teres f. maculata. DNA templates were prepared using the Extract-N-Amp Plant PCR Kits (Sigma Chemical Co., St. Louis, MO) and subjected to PCR using ITS1 and ITS4 primers. Amplicons were then purified and sequenced. The 585-bp nucleotide sequences of P. teres f. maculata from Mon-Dak area were submitted to GenBank under accession nos. PtmNES1 (JX187587), PtmSDY1 (JX187588), PtmSDY2 (JX187589), and PtmWIL1 (JX187590). The sequences from the four locations shared 100% similarity and also with P. teres f. maculata (EF452471) from GenBank while showing 10 nucleotide differences (99% similarity) with P. teres f. teres (EF452472).The results represent first report of SFNB in the Mon-Dak. Barley is one of the most important crops in the area. Resistance of the NFNB and SFNB of barley are controlled by different genes (4). Based on this report, SFNB therefore have to be considered in selection of barley cultivars for cultivation in the area. References: (1) H. E Bockelman et al. Plant Dis. 67:696, 1983. (2) R. T. Lartey et al. J. Sugar Beet Res. 40:1, 2003. (3) Z. H. Liu and T. L. Friesen. Plant Dis. 94:480, 2010. (4) O. M. Manninen et al. Genome. 46:1564, 2006.

Exotic dense-matter states pumped by a relativistic laser plasma in the radiation-dominated regime.

In high-spectral resolution experiments with the petawatt Vulcan laser, strong x-ray radiation of KK hollow atoms (atoms without n = 1 electrons) from thin Al foils was observed at pulse intensities of 3 × 10(20) W/cm(2). The observations of spectra from these exotic states of matter are supported by detailed kinetics calculations, and are consistent with a picture in which an intense polychromatic x-ray field, formed from Thomson scattering and bremsstrahlung in the electrostatic fields at the target surface, drives the KK hollow atom production. We estimate that this x-ray field has an intensity of >5 × 10(18) W/cm(2) and is in the 3 keV range.

Testing quantum mechanics in non-Minkowski space-time with high power lasers and 4(th) generation light sources.

A common misperception of quantum gravity is that it requires accessing energies up to the Planck scale of 10¹9 GeV, which is unattainable from any conceivable particle collider. Thanks to the development of ultra-high intensity optical lasers, very large accelerations can be now the reached at their focal spot, thus mimicking, by virtue of the equivalence principle, a non Minkowski space-time. Here we derive a semiclassical extension of quantum mechanics that applies to different metrics, but under the assumption of weak gravity. We use our results to show that Thomson scattering of photons by uniformly accelerated electrons predicts an observable effect depending upon acceleration and local metric. In the laboratory frame, a broadening of the Thomson scattered x ray light from a fourth generation light source can be used to detect the modification of the metric associated to electrons accelerated in the field of a high power optical laser.

Sex differences in the renal vascular response to angiotensin II involves the Mas receptor.

AIM: The renin-angiotensin system (RAS) depressor arm, particularly renal angiotensin type 2 receptor (AT(2) R) and Mas receptor (masR) expression, is enhanced in females, which may contribute to renal and cardiovascular protection. We examined the hypotheses that masR activation increases renal blood flow (RBF) at rest and attenuates the reduction in RBF in response to angiotensin II (AngII) infusion in female rats. Furthermore, we postulated that combined activation of the AT(2) R and masR would produce a greater response than masR activation alone. METHODS: In anaesthetized male and female Wistar rats, mean arterial pressure (MAP) and RBF responses during graded AngII infusion (30-1000 ng kg(-1)  min(-1) i.v.) were assessed following pre-treatment with vehicle, the masR antagonist A779, or A779 plus the AT(2) R antagonist PD123319. RESULTS: Basal MAP was not altered by any pre-treatment. Basal RBF decreased approx. 20% in female (P < 0.05), but not male rats in response to A779. However, basal RBF was not altered by A779 + PD123319. AngII infusion reduced RBF in a dose-related fashion (P(dose)  < 0.0001) and masR blockade did not alter the RBF response to AngII infusion in male or female rats. However, A779 + PD123319 attenuated the reduction in RBF response to AngII in females (P(group)  < 0.005), but not males. CONCLUSION: The impact of the masR on renal haemodynamics appears to be sexually dimorphic, with greater effects in female than male rats. However, the paradoxical effects of dual AT(2) R and masR blockade suggest that a greater understanding of the complex interactions between RAS components is required before the therapeutic opportunities of AT(2) R and/or masR stimulation can be advanced.

Evidence that renal arginine transport is impaired in spontaneously hypertensive rats.

Low renal nitric oxide (NO) bioavailability contributes to the development and maintenance of chronic hypertension. We investigated whether impaired l-arginine transport contributes to low renal NO bioavailability in hypertension. Responses of renal medullary perfusion and NO concentration to renal arterial infusions of the l-arginine transport inhibitor l-lysine (10 µmol·kg(-1)·min(-1); 30 min) and subsequent superimposition of l-arginine (100 µmol·kg(-1)·min(-1); 30 min), the NO synthase inhibitor N(G)-nitro-l-arginine (2.4 mg/kg; iv bolus), and the NO donor sodium nitroprusside (0.24 µg·kg(-1)·min(-1)) were examined in Sprague-Dawley rats (SD) and spontaneously hypertensive rats (SHR). Renal medullary perfusion and NO concentration were measured by laser-Doppler flowmetry and polarographically, respectively, 5.5 mm below the kidney surface. Renal medullary NO concentration was less in SHR (53 ± 3 nM) compared with SD rats (108 ± 12 nM; P = 0.004). l-Lysine tended to reduce medullary perfusion (-15 ± 7%; P = 0.07) and reduced medullary NO concentration (-9 ± 3%; P = 0.03) while subsequent superimposition of l-arginine reversed these effects of l-lysine in SD rats. In SHR, l-lysine and subsequent superimposition of l-arginine did not significantly alter medullary perfusion or NO concentration. Collectively, these data suggest that renal l-arginine transport is impaired in SHR. Renal l-[(3)H]arginine transport was less in SHR compared with SD rats (P = 0.01). Accordingly, we conclude that impaired arginine transport contributes to low renal NO bioavailability observed in the SHR kidney.

Superluminal sheath-field expansion and fast-electron-beam divergence measurements in laser-solid interactions.

We show that including a sufficient description of the target's rear surface significantly affects the interpretation of a wide range of laser-solid experiments. A simple Debye sheath model will be shown to be adequate. From this the sheath field responsible for ion acceleration has been shown to expand at superluminal speeds, leading to very large ion-emission regions on the target's rear surface; a new explanation for the dynamics of the ion-accelerating sheath field accounts for this observation and demonstrates the inaccuracy of measuring the angular divergence of the injected electron beam, crucial to fast ignition, from the lateral extent of the ion emission. However, it is shown that on careful probing the sheath field can provide unique insight into details of the fast electron's distribution function. The relative merits of probing other physical quantities has been examined. The width of the background temperature spot overestimates the divergence by a factor of 2 unless electron recirculation is prevented.

Fast advection of magnetic fields by hot electrons.

Experiments where a laser-generated proton beam is used to probe the megagauss strength self-generated magnetic fields from a nanosecond laser interaction with an aluminum target are presented. At intensities of 10(15) W cm(-2) and under conditions of significant fast electron production and strong heat fluxes, the electron mean-free-path is long compared with the temperature gradient scale length and hence nonlocal transport is important for the dynamics of the magnetic field in the plasma. The hot electron flux transports self-generated magnetic fields away from the focal region through the Nernst effect [A. Nishiguchi, Phys. Rev. Lett. 53, 262 (1984)] at significantly higher velocities than the fluid velocity. Two-dimensional implicit Vlasov-Fokker-Planck modeling shows that the Nernst effect allows advection and self-generation transports magnetic fields at significantly faster than the ion fluid velocity, v(N)/c(s)≈10.

Direct Polymerase Chain Reaction-Based Detection of Cercospora beticola in Field Soils.

Cercospora beticola, the causal agent of Cercospora leaf spot of sugar beet, survives as pseudostromata in infected sugar beet residues in the soil. Under optimal conditions, overwintering propagules germinate and produce conidia that are dispersed as primary inoculum to initiate infection in sugar beet. We developed a polymerase chain reaction (PCR) technique for rapid detection of C. beticola in field soils. Total DNA was first isolated from soil amended with C. beticola culture using the PowerSoil DNA Kit. The purified DNA was subjected to PCR in Extract-N-Amp PCR mix with CBACTIN primers over 35 cycles. The amplified products were resolved and compared by electrophoresis in 1% agarose gels. The PCR fragment size of C. beticola from the amended field soil correlated in size with the amplicon from control C. beticola culture DNA extract. Additionally, sample soils were collected from sugar beet fields near Sidney, MT and Foxholm, ND. Total DNA was extracted from the samples and subjected to PCR and resolved as previously described. The amplicons were purified from the gels and subjected to BigDye Terminator Cycle sequencing. All sequences from field soils samples, C. beticola-amended field soil, and pure culture were compared by alignment with a C. beticola actin gene sequence from GenBank. The result of the alignment confirmed the amplicons as products from C. beticola. Rapid screening for the presence of C. beticola in the soil by PCR will improve research capabilities in biological control, disease forecasting, and management of this very important sugar beet pathogen.

Effects of chronic sympatho-inhibition on reflex control of renal blood flow and plasma renin activity in renovascular hypertension.

BACKGROUND AND PURPOSE: We determined if chronic sympatho-inhibition with rilmenidine has functional significance for the kidney by altering responses of renal blood flow (RBF) and plasma renin activity (PRA) to stress and acute hypotension in rabbits with renovascular hypertension. EXPERIMENTAL APPROACH: RBF to each kidney and renal sympathetic nerve activity (RSNA) to the left kidney were measured in rabbits in which a renal artery clip induced hypertension (2K1C) and in sham-operated rabbits. After 2 weeks, a subcutaneous minipump was implanted to deliver rilmenidine (2.5 mg.kg(-1).day(-1)) to 2K1C rabbits for 3 weeks. KEY RESULTS: After 5 weeks of renal artery stenosis, mean arterial pressure (MAP) was 23% higher and PRA 3-fold greater than in sham-operated rabbits. Blood flow and renal vascular conductance in the stenosed kidney were lower (-75% and -80%) compared with sham, and higher in the non-clipped kidney (68% and 39%). Responses of RBF and PRA to hypotension were similar in 2K1C and sham rabbits. Airjet stress evoked a greater increase in MAP in 2K1C rabbits than sham controls. Chronic rilmenidine normalized MAP, reduced RSNA and PRA, and did not reduce RBF in the stenosed kidney. Responses of RBF (clipped and non-clipped kidney), RSNA and PRA to hypotension and airjet were little affected by rilmenidine. CONCLUSIONS AND IMPLICATIONS: Our observations suggest that chronic sympatho-inhibition is an effective antihypertensive therapy in renovascular hypertension. It normalizes MAP and reduces basal PRA without compromising blood flow in the stenosed kidney or altering responses of MAP, haemodynamics and PRA to acute hypotension and stress.