rAAV9 combined with renal vein injection is optimal for kidney-targeted gene delivery: conclusion of a comparative study.

Effective gene therapy strategies for the treatment of kidney disorders remain elusive. We report an optimized kidney-targeted gene delivery strategy using recombinant adeno-associated virus (rAAV) administered via retrograde renal vein injection in mice. Renal vein injection of rAAV consistently resulted in superior kidney transduction compared with tail vein injection using as little as half the tail vein dose. We compared rAAV5, 6, 8 and 9, containing either green fluorescent protein (GFP) or luciferase reporter genes driven by the Cytomegalovirus promoter. We demonstrated that although rAAV6 and 8 injected via renal vein transduced the kidney, transgene expression was mainly restricted to the medulla. Transgene expression was systematically low after rAAV5 injection, attributed to T-cell immune response, which could be overcome by transient immunosuppression. However, rAAV9 was the only serotype that permitted high-transduction efficiency of both the cortex and medulla. Moreover, both the glomeruli and tubules were targeted, with a higher efficiency within the glomeruli. To improve the specificity of kidney-targeted gene delivery with rAAV9, we used the parathyroid hormone receptor 'kidney-specific' promoter. We obtained a more efficient transgene expression within the kidney, and a significant reduction in other tissues. Our work represents the first comprehensive and clinically relevant study for kidney gene delivery.

Combined arteriovenous thrombolytic infusion for refractory renal vein thrombosis.

Acute renal vein thrombosis can rapidly lead to significant impairment and eventual loss of renal function. Classically presenting with flank pain, hematuria, and laboratory markers consistent with acute kidney injury, therapeutic anticoagulation is the mainstay of treatment. However, endovascular surgery offers a safe and effective alternative for renal salvage in the setting of acute renal vein thrombosis. Described is the use of combined arteriovenous thrombolytic infusion for refractory renal vein thromboses to quickly and effectively decrease clot burden in the micro- and macrovenous circulations while limiting systemic exposure.

Renal Vein Thrombosis After Open Repair of Abdominal Aortic Aneurysm Successfully Treated by Direct Oral Anticoagulants.

INTRODUCTION: Venous thromboembolism (VTE) of the lower extremities frequently occurs after surgery. It is unknown whether the complication of renal vein thrombosis (RVT) develops after an open repair (OR) for abdominal aortic aneurysm (AAA). Furthermore, anticoagulation therapy with apixaban, a direct oral anticoagulant (DOAC), has not been described as treatment for RVT in such cases. CASE: A 64-year-old man underwent OR for AAA. Postoperative computed tomography revealed RVT in the left renal vein. Apixaban (5 mg twice a day) therapy was initiated. Six months later, we discontinued anticoagulation therapy and observed no recurrence. Following OR, our patient developed RVT for which DOACs were very useful. CONCLUSION: Thus, RVT can manifest as VTE after OR and direct anticoagulants can be considered as a therapeutic option.

Balloon-Assisted Percutaneous Transhepatic Antegrade Embolization with 2-Octyl Cyanoacrylate for the Treatment of Isolated Gastric Varices with Large Gastrorenal Shunts.

AIMS: To evaluate the safety and effectiveness of percutaneous transhepatic antegrade embolization (PTAE) with 2-octyl cyanoacrylate assisted with balloon occlusion of the left renal vein or gastrorenal shunts (GRSs) for the treatment of isolated gastric varices (IGVs) with large GRSs. METHODS: Thirty patients with IGVs associated with large GRSs who had underwent PTAE assisted with a balloon to block the opening of the GRS in the left renal vein were retrospectively evaluated and followed up. Clinical and laboratory data were collected to evaluate the technical success of the procedure, complications, changes in the liver function using Child-Pugh scores, worsening of the esophageal varices, the rebleeding rate, and survival. Laboratory data obtained before and after PTAE were compared (paired-sample t-test). RESULTS: PTAE was technically successful in all 30 patients. No serious complications were observed except for one nonsymptomatic pulmonary embolism. During a mean follow-up of 30 months, rebleeding was observed in 4/30 (13.3%) patients, worsening of esophageal varices was observed in 4/30 (13.3%) patients, and newly developed or aggravated ascites were observed on CT in 3/30 (10%) patients. Significant improvement was observed in Child-Pugh scores (p=0.009) and the international normalized ratio (INR) (p=0.004) at 3 months after PTAE. The cumulative survival rates at 1, 2, 3, and 5 years were 96.3%, 96.3%, 79.9%, and 79.9%, respectively. CONCLUSION: Balloon-assisted PTAE with 2-octyl cyanoacrylate is technically feasible, safe, and effective for the treatment of IGV associated with a large GRS.

Selective arterial dilatation by glyceryl trinitrate is not associated with nitric oxide formation in vitro.

AIMS: Glyceryl trinitrate (GTN) is the most commonly used anti-anginal agent, yet its mechanism of action has still to be fully established. Release of nitric oxide (NO) and the selectivity of GTN in the venous system are believed to be crucial to this drug's anti-anginal action. METHODS: Rat superior mesenteric arteries and renal veins were mounted in a wire myograph with an intraluminal NO microsensor. RESULTS: In the superior mesenteric arteries, GTN (1 nM to 10 microM) produced a dose-dependent vasodilatation without NO release, except at concentrations supramaximal for relaxation. GTN was found to be markedly less potent in a wide range of veins tested, and lowering the oxygen concentrations in the myograph to that of the venous system did not improve the venodilator activity of GTN. CONCLUSION: This is the first time that NO release from GTN has been monitored electrochemically in real time, simultaneously with vasodilatation. Unlike the endothelium-dependent vasodilator carbachol, NO could only be measured at concentrations of GTN that are supramaximal for relaxation. GTN was found to be arterioselective in vitro, even when oxygen levels were lowered to mimic those of the venous system in vivo.

Enhanced protection of the renal vascular endothelium improves early outcome in kidney transplantation: Preclinical investigations in pig and mouse.

Ischemia reperfusion injury is one of the major complications responsible for delayed graft function in kidney transplantation. Applications to reduce reperfusion injury are essential due to the widespread use of kidneys from deceased organ donors where the risk for delayed graft function is especially prominent. We have recently shown that coating of inflamed or damaged endothelial cells with a unique heparin conjugate reduces thrombosis and leukocyte recruitment. In this study we evaluated the binding capacity of the heparin conjugate to cultured human endothelial cells, to kidneys from brain-dead porcine donors, and to murine kidneys during static cold storage. The heparin conjugate was able to stably bind cultured endothelial cells with high avidity, and to the renal vasculature of explanted kidneys from pigs and mice. Treatment of murine kidneys prior to transplantation reduced platelet deposition and leukocyte infiltration 24 hours post-transplantation, and significantly improved graft function. The present study thus shows the benefits of enhanced protection of the renal vasculature during cold storage, whereby increasing the antithrombotic and anti-adhesive properties of the vascular endothelium yields improved renal function early after transplantation.

Nutcracker syndrome due to left renal vein compression by an aberrant right renal artery.

Classic nutcracker syndrome is caused by left renal vein compression between the superior mesenteric artery and aorta, leading to retrograde venous hypertension associated with such urinary abnormalities as hematuria or proteinuria. We describe a case of symptomatic nutcracker syndrome treated by means of stent placement in which hypertension in the left renal vein was caused by stenosis of this vein compressed by an aberrant right renal artery at a point closer to the inferior vena cava.

Use of Doppler ultrasonography in the assessment of bronchodilator response in acute bronchiolitis.

Measurement of the response of acute bronchiolitis (AB) to bronchodilators relies on clinical signs and pulse oximetry. We hypothesized that Doppler ultrasonographic indices of hepatic venous flow may prove to be an objective tool in the assessment of the effect of inhaled salbutamol in infants hospitalized for AB. Previously healthy infants hospitalized for their first episode of AB were prospectively studied. Composite clinical score (CCS, retractions plus wheezing/crackles) and hemoglobin oxygen saturation (SaO(2)) were measured before, and 15-min post-salbutamol nebulization (0.15 mg/kg, minimum 1.5 mg). Peak velocities at the middle hepatic vein (PV-HV) and right renal vein (PV-RV), as well as peripheral-to-middle hepatic vein transit time (TT) of an ultrasound contrast agent were also measured by Doppler ultrasonography pre- and post-nebulization. Nineteen infants were studied. Mean CCS decreased by 0.37 (95% confidence interval [CI]: 0.08-0.66, P = 0.015) and mean SaO(2) increased by 0.68% (95%CI: 0.17-1.19, P = 0.01) post-bronchodilator treatment. Mean TT increased by 9.54 sec (95%CI: 5.95-13.13, P < 0.0001) and PV-HV increased by 16.49 cm/sec (95%CI: 9.07-23.91, P = 0.0002); PV-RV did not change. TT (r = 0.51, P = 0.009), but not PV-HV, correlated negatively with CCS. There was a strong positive correlation between pre- and post-salbutamol TT values (r = 0.92, P < 0.0001). The most likely explanation for these findings is post-salbutamol abolishment of shunting at the pulmonary capillary bed. We conclude that the peripheral-to-middle hepatic vein prolongation of TT measured by Doppler ultrasonography after salbutamol administration in infants with AB can be used as a bedside tool in the objective assessment of clinical response to medication in these patients.

From the nutcracker-phenomenon of the left renal vein to the midline congestion syndrome as a cause of migraine, headache, back and abdominal pain and functional disorders of pelvic organs.

This paper presents the hypothesis, that pain and functional disturbances of organs which lie on the midline of the body might be caused by a venous congestion of these organs. Cause of their congestion is the participation of these organs (vertebral column, skull, brain, spinal medullary, uterus, prostate, left ovary/testis, urinary bladder rectum, vagina, urethra) in the collateral circulation of the left renal vein. In many patients with complaints of the above mentioned organs the left renal vein is compressed inside the fork formed by the superior mesenteric artery and the aorta. This so called nutcracker phenomenon is incompletely understood today. It can lead to a marked reduction of left renal perfusion and forces the left renal blood to bypass the venous compression site via abundant collaterals. These collaterals are often not sufficient. Their walls become stretched and distorted - varices with inflamed walls are formed. These dilated veins are painful, interfere with the normal organ's function and demand more space than usual. This way pain in the midline organs and functional derangement of the midline organs can occur. The term "midline congestion syndrome" seems appropriate to reflect the comprehensive nature of this frequent disorder. The rationale for this hypothesis is based on the novel PixelFlux-technique (www.chameleon-software.de) of renal tissue perfusion measurement. With this method a relevant decline of left renal cortical perfusion was measured in 16 affected patients before therapy (left/right ratio: 0.79). After a treatment with acetylsalicylic acid in doses from 15 to 200mg/d within 14-200 days a complete relief of so far long lasting therapy-resistant midline organ symptoms was achieved. Simultaneously the left/right renal perfusion ratio increased significantly to 1.24 (p=0.021). This improvement of left renal perfusion can be explained by a better drainage of collateral veins, diminution of their wall distension, thereby decline of their intramural inflammation, reduction of their mass effects (especially by the replaced spinal fluid inside the spinal canal and the skull), and altogether a reduction of pain and functional derangement in the affected midline organs. The proposed theory might influence the current understanding of such frequent and difficult to treat diseases as chronic back pain, headaches, frequent cystitis, enuresis, abdominal pain, flank pain and might spur new theories of arterial hypertension, placental insufficiency, prostate diseases and myelopathies.

Androgens potentiate renal vascular responses to angiotensin II via amplification of the Rho kinase signaling pathway.

OBJECTIVES: This study assessed whether the Rho kinase signaling pathway contributes to androgenic amplification of angiotensin II (Ang II) induced pressor and renal constrictor responses. METHODS: Mean arterial pressure (MAP) responses to angiotensin II receptor 1 (AT1) inhibition were measured in conscious male New Zealand genetically hypertensive rats (NZGH) subjected to sham operation, castration or castration+testosterone replacement. MAP and renal vascular resistance (RVR) responses to Ang II were recorded with and without a Rho kinase inhibitor, fasudil, in anesthetized NZGH. Western blot was used to analyze target protein expression in the kidney. RESULTS: MAP responses to AT1 receptor inhibition and exogenous Ang II were attenuated in castrated NZGH. The increase in RVR (mm Hg/ml/min/g kidney) at the maximum dose of Ang II was significantly lower in castrated NZGH than in sham operated NZGH. Testosterone replacement restored RVR responses to Ang II in castrated rats. Fasudil treatment reduced both MAP and RVR responses to Ang II in each group. In addition, the differential MAP and RVR responses to Ang II amongst the three groups were significantly attenuated by Rho kinase inhibition. Western blot showed that Rho kinase protein expression was reduced by castration, while testosterone replacement restored the Rho kinase protein levels in castrated rats. The phosphorylation of myosin phosphatase target subunit 1 (MYPT1), a downstream target of Rho kinase, was also increased by androgens. CONCLUSIONS: Collectively, these results indicate that androgens potentiate Ang II-induced renal vascular responses, an effect mediated at least partly via up-regulation of the Rho kinase signaling pathway.

Renal and femoral venous blood flows are regulated by different mechanisms dependent on α-adrenergic receptor subtypes and nitric oxide in anesthetized rats.

Venous and arterial walls are responsive to sympathetic system and circulating substances, nevertheless, very few is known about the venous blood flow regulation simultaneously to arterial vascular beds. In this study, we compared the venous and arterial blood flow regulation in visceral and muscular beds upon injection of different doses of vasoactive drugs which act in arterial vascular beds. Anesthetized adult male Wistar rats underwent to right femoral artery and vein cannulation for hemodynamic recordings and infusion of drugs. Doppler flow probes were placed around the left renal artery and vein, and left femoral artery and vein to evaluate the changes in flood flow. Phenylephrine (PHE) injection (α1-adrenergic receptor agonist) elicited vasoconstriction in all arteries and veins. Intravenous prazosin (PZS) (1mg/kg, α1-adrenergic receptor blocker) caused renal artery vasodilation, but not in the other beds. Vasoconstrictor effect of PHE was abolished by PZS in all vascular beds, except in femoral vein. Phentolamine (PTL) injection (1mg/kg, α1/α2-adrenergic receptor blocker) produced renal artery vasodilation with no change in other beds. After PTL, the vasoconstriction evoked by PHE was abolished in all vascular beds. Sodium Nitroprusside (SNP), a nitric oxide donor, elicited vasodilation in all beds, and after PTL but not post PZS injection, SNP enhanced the vasodilatory effect in femoral vein. Our findings suggest that the vasoconstriction in renal and femoral veins is mediated by different subtypes of α-adrenoceptors. The nitric oxide-dependent vasodilation in femoral vein enhances when α2-adrenoceptors are not under stimulation, but not in the other vascular beds investigated.

Successful outpatient treatment of renal vein thrombosis by low-molecular weight heparins in 3 patients with nephrotic syndrome.

Renal vein thrombosis (RV Thromb) is a serious complication ofnephrotic syndrome. Anticoagulation is usually recommended as the treatment of choice. This study reports 3 nephrotic patients diagnosed to have RVThromb combined with thromboembolic events. Low-molecular weight heparin (LMWHep) was given subcutaneously every 12 hours following the diagnosis of RVTromb, which continued at the outpatient clinic after an average of 11 in-hospital days. The patients visited the nephrology outpatient clinic every other week and underwent magnetic resonance image (MRI) studies at 6-week intervals for follow-up of patency of the involved renal vein. LMWHep was discontinued when MRI showed this patency. The average outpatient treatment period was 74 days. There was no recurrent RVThromb in the follow-up course of 6 months after discontinuation of LMWHep. Kidney function was preserved, as indicated by image studies and serial renal function tests. LMWHep produced a more predictable anti-coagulant effect, a superior bioavailability, a longer half-life and a dose-independent effect than unfractionated heparin and coumadin. These benefits made the outpatient treatment of RVThromb possible. Our report recommends outpatient treatment of RVThromb by LMWHep because it is feasible, effective and safe.

Anticoagulation therapy for the prevention of hemodialysis tunneled cuffed catheters (TCC) thrombosis.

BACKGROUND: Chronic oral anticoagulation is currently used to avoid thrombosis and the malfunction of tunneled cuffed catheters (TCCs) for hemodialysis (HD). The aim of the study was to assess the efficacy of early warfarin administration, after TCC placement, in comparison to its administration after the first thrombosis or malfunction event of the TCC. PATIENTS AND METHODS: One hundred and forty-four chronic dialysis patients, who underwent TCC placement between June 2001 and June 2005, were randomized into two groups: 81 patients, group A, started oral anticoagulation 12 hr after the TCC placement (target international normalized ratio (INR) 1.8-2.5), in association with ticlopidine 250 mg/die; 63 patients, group B, started warfarin after the first thrombosis/malfunction episode (target INR 1.8-2.5) in association with ticlopidine 250 mg/die. The efficacy of oral anticoagulation therapy in preventing TCC thrombotic complications was evaluated in a 12-month follow-up period, after TCC placement, in terms of: a) the number of patients with thrombotic-malfunction events; b) the number of thrombotic-malfunction events with urokinase infusion (events/patient/year); c) intradialytic blood flow rate (BFR, ml/min); d) negative blood pressure (BP) from the arterial line of the TCC (AP, mmHg); e) positive BP, in the extracorporeal circuit from the venous line (VP, mmHg); and f) bleeding complications. RESULTS: Ten patients (12%) in group A showed TCC thrombosis/malfunction vs. 33 patients (52%) in group B (p < 0.01). In group A, 0.16 events of thrombosis/malfunction per patient/year vs. 1.65 in group B (p < 0.001) were ob-served. BFR was respectively 305 +/- 34 vs. 246 +/- 42 ml/min (p < 0.001). AP was -124 +/- 13 in group A vs. -174 +/- 21 mmHg in group B (p < 0.05). VP was 112 +/- 28 in group A vs. 168 +/- 41 mmHg in group B (p < 0.05). No patient showed any bleeding events. CONCLUSIONS: Early warfarin therapy allows a significant reduction in TCC thrombotic complications and an improvement in both arterial and venous fluxes in comparison with the same therapy administered after the first TCC thrombotic/malfunction event. This therapy did not induce any bleeding complications in the patients included in the study.

Renal hemodynamic effects of vasodilation with nifedipine and hydralazine in patients with heart failure.

The central and renal hemodynamic effects of nifedipine were evaluated in nine patients with severe chronic congestive heart failure. Oral nifedipine (34 +/- 22 mg, mean +/- standard deviation) was associated with a decrease in systemic vascular resistance from 1,748 +/- 436 to 1,321 +/- 302 dynes . s . cm-5 (p less than 0.001) and mean arterial blood pressure from 96 +/- 11 to 87 +/- 6 mm Hg (p less than 0.05) and with an increase in cardiac output from 4.2 +/- 1.1 to 4.9 +/- 1.2 liters/min (p less than 0.001). Although renal vascular resistance decreased from 11,988 +/- 2,256 to 10,286 +/- 3,011 dynes . s . cm-5 (p less than 0.05), no significant change was seen in renal blood flow (599 +/- 120 to 640 +/- 162 ml/min), glomerular filtration rate (62 +/- 18 to 62 +/- 17 ml/min), filtration fraction (18 +/- 5 to 17 +/- 6%), the ratio of renal/systemic vascular resistance (7.0 +/- 1.0 to 7.9 +/- 1.8) and the ratio of renal blood flow/cardiac output (0.15 +/- 0.02 to 0.13 +/- 0.03). Intravenous hydralazine (10 +/- 5 mg), given to eight of the patients in a randomized crossover design, resulted in a larger increase in cardiac output than did nifedipine (38 +/- 7 versus 19 +/- 10%, p less than 0.001) and in an increase in total renal blood flow from 570 +/- 152 to 645 +/- 174 ml/min (p less than 0.001). Renal vascular resistance decreased from 12,080 +/- 2,934 to 10,153 +/- 2,372 dynes . s . cm-5 (p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Preservation Solution Effluent Osmolality as a Predictor of Initial Kidney Transplant Dysfunction.

OBJECTIVES: The aim of this study was to identify new predictors of kidney graft primary dysfunction from results of metabolic, electrolyte composition, and preservation solution effluent osmolality analyses of kidneys from deceased donors. MATERIALS AND METHODS: Samples of left renal veins in Custodiol preservation solution (produced by Dr. F. Kohler, Chemie, Bensheim, Germany) from kidney explants and from back table surgical procedures were obtained from 55 deceased donors. We compared metabolic parameters (glucose and lactate levels), electrolyte composition (potassium, sodium, calcium, chlorine), and effluent osmolality of kidney samples from donors whose recipients had satisfactory initial graft function (n = 44) and dysfunction (n = 22). Values are shown as median and interquartile ranges between the 25th and 75th percentiles. We used the Mann-Whitney U test to compare quantitative variables. RESULTS: Statistically significant differences were observed in effluent osmolality results between kidneys that resulted in satisfactory graft function (median, 85; interquartile range, 65.5-97.1) and those that did not result in satisfactory graft function (median, 103.25; interquartile range, 78.7-125.75) (P = .045). We also observed a trend toward significance in sodium ion levels (P = .073) and lactate levels (P = .09). No statistically significant differences were shown in samples obtained from the back table surgical procedure. CONCLUSIONS: As a predictor of an initially satisfactory functioning deceased-donor kidney graft, it is possible to use the level of osmolality in Custodiol solution effluent obtained at explant.

Increase in collateral arterial endothelial cell proliferation induced by captopril after renal artery stenosis in the rat.

Studies to assess the role of blood pressure rise in the growth of the collateral arterial supply following renal artery stenosis were performed in 70 rats. Assessment of the proliferative response was made by coded reading of endothelial cell turnover following tritiated thymidine administration, 5 days after renal artery stenosis. Stenosis induced the anticipated brisk increase in endothelial cell turnover in arterial collaterals and in the ipsilateral renal vein, and ureteric epithelium. Blood pressure elevation did not appear to play the dominant role, as the proliferative response did not parallel blood pressure changes; moreover, neither bilateral renal artery stenosis, designed to enhance the hypertension, nor hydralazine administration, to reduce the blood pressure, influenced endothelial cell turnover. A contribution of elevated blood pressure to the vasoproliferative response, however, was not ruled out definitively in this study. Captopril, also administered to assess the same question, resulted in an enhanced endothelial cell proliferative response, both in frequency and in degree, an observation that became the central thrust of our study. The mechanism by which converting enzyme inhibitor modified endothelial cell turnover is not clear, but may well provide insight into the responsible factors.

Renal adaptation to sodium deprivation. Effect of captopril in the rat.

Dietary sodium restriction is associated with a rapid decrease in urinary sodium excretion and achievement of a new sodium balance within three to five days. In addition, renal vasoconstriction and progressive activation of intrarenal systems with vasoconstrictor (renin-angiotensin) or vasodilating (kallikrein-kinin and prostaglandins) properties are observed. The relationship between sodium homeostasis and the renin-angiotensin system was assessed through the use of captopril in the rat. Treatment with captopril, before and during a six-day period after suppression of dietary sodium, was associated with sodium wasting (urinary sodium always exceeded sodium intake during the observation period); in addition, the normal increase in urinary aldosterone was blunted by about 80 percent. When captopril treatment was given for six days to rats maintained on long-term sodium restriction (at least four weeks) urinary sodium increased, although transiently; at the end of the study, renal vasodilatation together with a redistribution of glomerular blood flow to nonsuperficial glomeruli was observed. These studies indicate that captopril administration markedly blunts the renal and systemic adaptations to a reduced sodium intake in the rat. They suggest that the renin-angiotensin system is probably indispensable in preventing sodium loss when dietary sodium is suppressed.

An examination of the postjunctional alpha-adrenoceptor subtypes for (-)-noradrenaline in several isolated blood vessels from the rabbit.

1. Postjunctional alpha-adrenoceptors in several isolated blood vessels from the rabbit have been characterized on the basis of the relative potency of the agonists noradrenaline (NA, non-selective), phenylephrine (alpha 1-selective) and UK-14304 (alpha 2-selective), and the potency of antagonists rauwolscine (alpha 2-selective) and corynanthine (alpha 1-selective) against contractions elicited by NA. In addition, the potency of prazosin against NA was also assessed in the venous preparations. 2. The thoracic aorta, ear artery and left renal vein appear to possess alpha 1-adrenoceptors since the agonist potency order was NA greater than phenylephrine greater than UK-14304, while corynanthine was 3-10 fold more potent than rauwolscine. 3. The ear vein appears to possess alpha 2-adrenoceptors. The rank order of agonist potency was UK-14304 greater than NA much greater than phenylephrine and all three agonists elicited responses of similar magnitude. Furthermore, rauwolscine was 30 fold more potent than corynanthine while prazosin failed to produce a concentration-dependent inhibition. 4. The saphenous vein and the plantaris vein appear to possess a mixture of both subtypes since the rank order of agonist potency was UK-14304 greater than NA much greater than phenylephrine, while responses elicited by UK-14304 were smaller than those to the other agonists. However, although rauwolscine was 20 to 100 fold more potent than corynanthine in both preparations, suggestive of predominantly alpha 2-adrenoceptors, prazosin was either potent (saphenous vein) or relatively inactive (plantaris vein). 5. The characteristics of postjunctional alpha 1- and alpha 2-adrenoceptors on isolated blood vessels from the rabbit are discussed in relation to the value of both the agonists, particularly NA, and the antagonists used in this study.

Vasoconstrictor endothelin receptors characterized in human renal artery and vein in vitro.

1. We have identified the endothelin receptors present in the media of human main stem renal artery and vein and characterized the subtypes mediating vasoconstriction in these blood vessels in vitro. 2. Messenger RNA encoding both ETA and ETB receptors was identified in the smooth muscle layer of human renal artery and vein by reverse transcriptase-polymerase chain reaction assay. In cryostat-cut cross-sections of both vessels autoradiographical visualisation suggested a majority of ETA receptors. Intense binding was obtained to the non-selective ligand [125I]-ET-1 and the ETA-selective [125I]-PD151242 but only weak labelling of sites by the ETB-selective [125I]-BQ3020. 3. ET-1 potently constricted renal artery and vein preparations with EC50 values of 4.06 nM and 1.00 nM, respectively. Sarafotoxin 6b was approximately ten times less potent than ET-1 with EC50 values of 36.3 nM and 13.8 nM respectively. In the renal artery, ET-3 and sarafotoxin 6c showed little or no activity up to 300 nM. Responses to these peptides were more variable in the renal vein. Preparations from three individuals did not respond to ET-3 but in three further cases, although ET-3 was much less potent than ET-1, full dose-response curves were obtained. S6c elicited dose-related contractions in vein preparations from 5/6 individuals and although more potent than ET-1, the maximum response was 30-60% of that obtained to ET-1. 4. ET-1-induced vasoconstriction of renal artery and vein was antagonized by the ETA-selective, BQ123 (3-10 microM). The dose-response curves to ET-1 were displaced in a parallel rightward fashion with no attenuation of the maximum responses. pA2 values were estimated to be 6.8 +/- 0.1 and 6.8 +/- 0.4 for artery and vein respectively.5. These data suggest that mRNA encoding both ETA and ETB receptors is present in the media of human main stem renal artery and vein. However, autoradiographical studies indicate that the majority of ET receptors expressed are of the ETA subtype. The relative potencies of ET-1 and ET-3 as vasoconstrictors of renal blood vessels in vitro is consistent with this being an ETA-mediated response,and therefore whilst responses to S6c indicate that constrictor ETB receptors may be present in renal veins from some individuals these are likely to be of less importance in these blood vessels.

Effects of adrenoceptor agonists and antagonists on smooth muscle cells and neuromuscular transmission in the guinea-pig renal artery and vein.

In the guinea-pig renal artery and vein, the membrane potential was -66.8 mV and -46.8 mV, the length constant 0.54 mm and 0.43 mm, and the time constant 240 ms and 98 ms, respectively. The maximum slope of the depolarization produced by a 10 fold increase [K]o was 46 mV in the renal artery and 39 mV in the renal vein. Noradrenaline (NA over 5 X 10(-7)M in the artery and over 10(-7)M in the vein) depolarized the membrane and slightly reduced the membrane resistance, assessed from relative changes in the amplitude of electrotonic potential. The action of NA was suppressed by prazosin in the artery but by yohimbine in the vein, i.e. the alpha 1-adrenoceptor is present in the extrajunctional muscle membrane in the renal artery while the alpha 2-adrenoceptor is present in the renal vein. Dopamine and isoprenaline did not modify the membrane properties. In the renal artery, repetitive perivascular nerve stimulation (0.1 ms, 50 Hz, 5 shocks) evoked excitatory junction potential (e.j.p.). Applications of guanethidine (10(-6) M) or tetrodotoxin (3 X 10(-7) M) abolished the generation of the e.j.p.. Low concentrations of phentolamine (5 X 10(-7) M), prazosin (10(-7) M) and yohimbine (5 X 10(-7) M) enhanced the e.j.p. amplitude, while high concentrations of phentolamine (10(-5) M) and prazosin (greater than 10(-5) M) reduced the amplitude of e.j.p.s. NA, dopamine and clonidine consistently suppressed the amplitude of e.j.ps, at any given concentration over 10(-7) M. Spontaneous generated miniature e.j.ps (m.e.j.ps) were recorded on rare occasions. Phentolamine and yohimbine both at 5 x 10(-7) M and prazosin 10(-7) M increased the appearance of m.e.j.ps. 5 In the renal vein, repetitive nerve stimulation failed to generate the e.j.p. Sympathetic innervation to this tissue seems to be sparse. 6 Specificity of innervation and adrenoceptors present on smooth muscle cells in both the renal artery and vein are discussed, and the presynaptic regulation ofNA release is compared with findings in other vascular tissues.