Changes In Endothelin Research Articles

Vasoactive Biomarkers in Patients With Vasovagal Syncope During Head-Up Tilt Test: A Case-Control Study.

Background:Vasovagal syncope (VVS) is the most common cause of syncope. Some stages of its pathophysiological mechanisms remain unclear. Vasoactive substances such as nitric oxide metabolites (NOx) and endothelin (ET) may be involved during acute orthostatic stress.Objective:To analyze plasma changes in NOx and ET and heart rate variability (HRV) in the supine positions (T1) and during the head-up tilt test (HUTT) (T2), in patients with VVS (case group) and control group.Methods:Thirty-seven patients (17 in the case group and 20 in the control group), matched for age and sex (mean aged 31.8 years) underwent HUTT with simultaneous HRV recording and venipuncture. Blood samples were collected during phases T1 and T2 and the analysis was performed without knowledge of the HUTT result.Results:In the total sample, there was an increase in NOx values (P = .014), however there was no increase in ET values from phase T1 to phase T2. Patients with VVS tended to increase plasma NOx values (P = .057) and had significantly higher plasma values compared to ET (P = .033) between phases T1 to T2. In the control group, there was no significant change in the values of these vasoactive substances. Regarding HRV, there were a decrease in the component HF (high frequency) and increased of the LF (low frequency)/HF ratio during HUTT.Conclusions:There was an increase in ET during HUTT occurred only in the case group. These patients are more likely to have an imbalance between antagonistic vasoactive biomarkers during orthostatic stress.

Ovariectomy Reduces Vasocontractile Responses of Rat Middle Cerebral Arteries After Focal Cerebral Ischemia.

Effects of sex hormones on stroke outcome are not fully understood. A deleterious consequence of cerebral ischemia is upregulation of vasoconstrictor receptors in cerebral arteries that exacerbate stroke injury. Here, we tested the hypothesis that female sex hormones alter vasocontractile responses after experimental stroke in vivo or after organ culture in vitro, a model of vasocontractile receptor upregulation. Female rats with intact ovaries and ovariectomized (OVX) females treated with 17β-estradiol, progesterone, or placebo were subjected to transient, unilateral middle cerebral artery occlusion followed by reperfusion (I/R). The maximum contractile response, measured my wire myography, in response to the endothelin B receptor agonist sarafotoxin 6c was increased in female arteries after I/R, but the maximum response was significantly lower in arteries from OVX females. Maximum contraction mediated by the serotonin agonist 5-carboxamidotryptamine was diminished after I/R, with arteries from OVX females showing a greater decrease in maximum contractile response. Contraction elicited by angiotensin II was similar in all arteries. Neither estrogen nor progesterone treatment of OVX females affected I/R-induced changes in endothelin B- and 5-carboxamidotryptamine-induced vasocontraction. These findings suggest that sex hormones do not directly influence vasocontractile alterations that occur after ischemic stroke; however, loss of ovarian function does impact this process.

Effect of bariatric surgery on inflammation and endothelial dysfunction as processes underlying subclinical atherosclerosis in morbid obesity.

Inflammation and endothelial dysfunction are associated with morbid obesity (MO) and atherosclerosis. To evaluate inflammation and endothelial function as the initial mechanisms underlying subclinical atherosclerosis in patients with MO, with and without atheromas, and their evolution after bariatric surgery (BS). Arnau de Vilanova University Hospital and University of Barcelona. Plasma samples from 66 patients with MO were obtained before BS and 6 and 12 months after BS. Patients were divided into 2 groups based on the presence of atheromatous plaques (detected by ultrasound imaging). Inflammation was increased as demonstrated by changes in the levels of fibroblast growth factor 21, adiponectin, leptin, interleukin 6, tumor growth factor α, nonesterified free fatty acids, lipoprotein(a) and C-reactive protein (CRP). Endothelial dysfunction was characterized by impaired angiogenesis (measured through angiopoietin 1 and 2 and brain-derived neurotrophic factor), vascular function (changes in endothelin 1 and thrombomodulin levels), and diapedesis (changes in intercellular and vascular cell adhesion molecules, and E- and P-selectins). Both mechanisms occurred regardless of the presence of atheromas. BS ameliorated both processes even in patients who already had subclinical atherosclerosis. However, CRP, thrombomodulin, and P-selectin levels were higher in patients with atheromas. Endothelial dysfunction and inflammation were detected before the appearance of structural changes in vessel walls on ultrasonography images. BS might prevent or slow atherogenesis in the early stages by breaking the vicious circle between inflammation and endothelial dysfunction. CRP, thrombomodulin, and P-selectin may have a critical role in plaque development and, together with the study of endothelial dysfunction, might be useful in assessing early atherosclerosis and its evolution after BS.

Naringin inhibits vascular endothelial cell apoptosis via endoplasmic reticulum stress‑ and mitochondrial‑mediated pathways and promotes intraosseous angiogenesis in ovariectomized rats

In this study, to investigate the effects of naringin on vascular endothelial cell (VEC) function, proliferation, apoptosis, and angiogenesis, rat VECs were cultured in vitro and randomly divided into four groups: control, serum-starved, low-concentration naringin treatment, and high-concentration naringin treatment. MTT assay was used to detect cell proliferation while Hoechst 33258 staining and flow cytometry were used to detect apoptosis. Changes in the expression of apoptosis-associated proteins [GRP78, CHOP, caspase-12, and cytochrome c (Cyt.c)] were detected using western blotting. JC-1 staining was employed to detect changes in mitochondrial membrane potential. Intracellular caspase-3, -8, and -9 activity was determined by spectrophotometry. ELISA was used to detect endothelin (ET), and a Griess assay was used to detect changes in the expression of nitric oxide (NO) in culture medium. The study further divided an ovariectomized (OVX) rat model of osteoporosis randomly into four groups: OVX, sham-operated, low-concentration naringin treatment (100 mg/kg), and high-concentration naringin treatment (200 mg/kg). After 3 months of treatment, changes in serum ET and NO expression, bone mineral density (BMD), and microvessel density of the distal femur (using CD34 labeling of VECs) were determined. At each concentration, naringin promoted VEC proliferation in a time- and dose-dependent manner. Naringin also significantly reduced serum starvation-induced apoptosis in endothelial cells, inhibited the expression of GRP78, CHOP, caspase-12, and Cyt.c proteins, and reduced mitochondrial membrane potential as well as reduced the activities of caspase-3 and -9. Furthermore, naringin suppressed ET in vitro and in vivo while enhancing NO synthesis. Distal femoral microvascular density assessment showed that the naringin treatment groups had a significantly higher number of microvessels than the OVX group, and that microvascular density was positively correlated with BMD. In summary, naringin inhibits apoptosis in VECs by blocking the endoplasmic reticulum (ER) stress- and mitochondrial-mediated pathways. Naringin also regulates endothelial cell function and promotes angiogenesis to exert its anti-osteoporotic effect.

Upregulation of the endothelin A (ETA) receptor and its association with neurodegeneration in a rodent model of glaucoma

BackgroundPrimary open angle glaucoma is a heterogeneous group of optic neuropathies that results in optic nerve degeneration and a loss of retinal ganglion cells (RGCs) ultimately causing blindness if allowed to progress. Elevation of intraocular pressure (IOP) is the most attributable risk factor for developing glaucoma and lowering of IOP is currently the only available therapy. However, despite lowering IOP, neurodegenerative effects persist in some patients. Hence, it would be beneficial to develop approaches to promote neuroprotection of RGCs in addition to IOP lowering therapies. The endothelin system is a key target for intervention against glaucomatous neurodegeneration. The endothelin family of peptides and receptors, particularly endothelin-1 (ET-1) and endothelin B (ETB) receptor, has been shown to have neurodegenerative roles in glaucoma. The purpose of this study was to examine changes in endothelin A (ETA) receptor protein expression in the retinas of adult male Brown Norway rats following IOP elevation by the Morrison’s model of ocular hypertension and the impact of ETA receptor overexpression on RGC viability in vitro.ResultsIOP elevation was carried out in one eye of Brown Norway rats by injection of hypertonic saline through episcleral veins. After 2 weeks of IOP elevation, immunohistochemical analysis of retinal sections from rat eyes showed an increasing trend in immunostaining for ETA receptors in multiple retinal layers including the inner plexiform layer, ganglion cell layer and outer plexiform layer. Following 4 weeks of IOP elevation, a significant increase in immunostaining for ETA receptor expression was found in the retina, primarily in the inner plexiform layer and ganglion cells. A modest increase in staining for ETA receptors was also found in the outer plexiform layer in the retina of rats with IOP elevation. Cell culture studies showed that overexpression of ETA receptors in 661W cells as well as primary RGCs decreases cell viability, compared to empty vector transfected cells. Adeno-associated virus mediated overexpression of the ETA receptor produced an increase in the ETB receptor in primary RGCs.ConclusionsElevated IOP results in an appreciable change in ETA receptor expression in the retina. Overexpression of the ETA receptor results in an overall decrease in cell viability, accompanied by an increase in ETB receptor levels, suggesting the involvement of both ETA and ETB receptors in mediating cell death. These findings raise possibilities for the development of ETA/ETB dual receptor antagonists as neuroprotective treatments for glaucomatous neuropathy.

Effect of Low Versus High Dialysate Sodium Concentration on Blood Pressure and Endothelial-Derived Vasoregulators During Hemodialysis: A Randomized Crossover Study

Intradialytic hypertension affects ∼15% of hemodialysis patients and is associated with increased morbidity and mortality. While intradialytic hypertension is associated with increases in endothelin 1 relative to nitric oxide (NO), the cause of these imbalances is unknown. Invitro evidence suggests that altering plasma sodium levels could affect endothelial-derived vasoregulators and blood pressure (BP). Thus, we hypothesized that compared to high dialysate sodium, low dialysate sodium concentration would lower endothelin 1 levels, increase NO release, and reduce BP. 3-week, 2-arm, randomized, crossover study. 16 patients with intradialytic hypertension. Low (5 mEq/L below serum sodium) versus high (5 mEq/L above serum sodium) dialysate sodium concentration. Endothelin 1, nitrite (NO2(-)), and BP. Mixed linear regression was used to compare the effect of dialysate sodium (low vs high) and randomization arm (low-then-high vs high-then-low) on intradialytic changes in endothelin 1, NO2(-), and BP values. The average systolic BP throughout all hemodialysis treatments in a given week was lower with low dialysate sodium concentrations compared with treatments with high dialysate sodium concentrations (parameter estimate,-9.9 [95% CI,-13.3 to-6.4] mm Hg; P< 0.001). The average change in systolic BP during hemodialysis also was significantly lower with low vs high dialysate sodium concentrations (parameter estimate,-6.1 [95% CI,-9.0 to-3.2] mm Hg; P< 0.001). There were no significant differences in intradialytic levels of endothelin 1 or NO2(-) with low vs high dialysate sodium concentrations. Carryover effects limited the power to detect significant changes in endothelial-derived vasoregulators, and future studies will require parallel trial designs. Low dialysate sodium concentrations significantly decreased systolic BP and ameliorated intradialytic hypertension. Longer studies are needed to determine the long-term effects of low dialysate sodium concentrations on BP and clinical outcomes.

Protection of Vascular Endothelial Cells Injured by Angiotensin II and Hypoxia In Vitro by Ginkgo biloba (Ginaton)

The objective of this study was to explore the protective effect and the possible mechanism of Ginkgo biloba extract (Ginaton) on human vascular endothelial cells (VECs) injured by angiotensin II (Ang-II) and hypoxia. The human aortic VECs were divided into different groups to observe the changes in endothelin (ET), calcium concentration ([Ca(2+)]i), and mitochondrial membrane potential (MMP). The results showed that Ginaton had inhibited ET secretion induced by hypoxia and Ang-II (P < .01). the protection offered by Ginaton at mid (10 mg/mL) and low (5 mg/mL) concentrations was obviously better than that offered at high concentration (25 mg/mL). The [Ca(2+)]i increased and MMP decreased significantly in both hypoxia group and Ang-II group (P < .01); however, the changes in [Ca(2+)]i and MMP could be meliorated by Ginaton. This study suggested that Ginaton could effectively protect VECs against injury, and the dose used clinically would rather be low than too high for getting better results.

Protective Effects of Ginaton on Vascular Endothelial Cells Injured by Angiotensin II and Hypoxia In Vitro

The objective of this study was to explore the protective effect and possible mechanism of Ginkgo biloba extract (Ginaton) on human vascular endothelial cells (VECs) injured by angiotensin II (Ang-II) and hypoxia. The human aortic VECs were divided into different groups to observe the changes in endothelin (ET), intracellular calcium concentration ([Ca(2+)]i), and mitochondrial membrane potential (MMP). The results showed that Ginaton had inhibited ET secretion induced by hypoxia and Ang-II (P < .01); the protective effects of mid (10 mg/mL) and low concentrations (5 mg/mL) of Ginaton was obviously higher than that of the high concentration (25 mg/mL); [Ca(2+)]i increased and MMP decreased significantly in both the hypoxia and the Ang-II groups (P < .01); however, the changes in [Ca(2+)]i and MMP could be meliorated by Ginaton. This study suggested that Ginaton could effectively protect VECs against injury, and lower dose would be used clinically rather than the higher dose for obtaining better results.

Effects of exercise intervention on vascular endothelium functions of patients with impaired glucose tolerance during prediabetes mellitus

Endothelial dysfunction (ED) is an early pathophysiological change in patients with impaired glucose tolerance (IGT) during prediabetes mellitus. This study was designed to test the hypothesis that exercise intervention contributes to the reversal of vascular endothelium-dependent dysfunction in middle-aged patients with IGT. Following exercise intervention, significant changes in endothelin (ET)-1, C-type natriuretic peptide (CNP), ΔDia-P, oral glucose tolerance test (OGTT)2h, fasting insulin, homeostasis model of assessment-insulin resistance (HOMA-IR), body fat percentage, waist circumference and waist to hip ratio were measured. However, no marked changes in carotid artery intima-media thickness (IMT), fasting blood glucose and BMI were observed following exercise intervention. Validity analysis of index changes in the two exercise intervention groups further confirmed there was no change. Exercise intervention increased CNP levels, decreased ET-1 levels and increased ΔDia-P, indicating improved vascular endothelium function. Decreased HOMA-IR following exercise suggests enhanced insulin sensitivity. Exercise intervention also improved glucose metabolism via decreased OGTT2h and fasting insulin. In addition, decreased waist circumference, ratio of waist to hip and body fat percentage following exercise intervention improved changes of body composition, including BMI, body fat and waist circumference. These results indicate that exercise intervention may reverse vascular endothelium-dependent dysfunction in middle-aged patients with IGT. This study also provided direct clinical data supporting the use of exercise intervention to prevent diabetes mellitus (DM) during the early stage.

Vliyanie sulodeksida na funktsional'noe sostoyanie endoteliya u bol'nykh s sakharnym diabetom i diabeticheskoyretinopatiey

Aim. To study effect of sulodexide (Vessel Due F) on the functional state of endothelium in patients with diabetic retinopathy. Materials and methods. A total of 37 patients with DR were divided in 2 groups and treated with sulodexide. Group 1 comprised 16 patients withnon-proliferative DR, group 2 included 21 patients with preproliferative DR. The functional state of endothelium was estimated from the plasma andserum levels of endothelial factors (sVCAM, endothelin, nitric oxide, t-PA, Willebrand factor). Results. The measurement of the initial levels of endothelial factors in both groups revealed significant changes in endothelin, nitric oxide, and sVCAMsuggesting disturbances of endothelial function due to DR. Sulodexide therapy normalized it regardless of DR stage and thereby improved functionalactivity of retina. Conclusion. This study has demonstrated beneficial effect of sulodexide on endothelial function in patients with DR due to correction of the productionof vasoactive factors (endothelin, nitric oxide) and stimulation of fibrinolytic activity of the vascular wall (t-PA).

Changes in endothelin and nitric oxide during hemorrhagic shock-volume resuscitation and their relationships with renal function in pigs

Objective To evaluate the changes in plasma endothelin (ET) and nitric oxide (NO) concentrations during hemorrhagic shock and volume resuscitation (HS-VR) and investigate their relationships with renal function in pigs. Methods Fourteen male pigs weighing 14-17 kg were randomly divided into 2 groups (n=7 each): sham operation group (S) and HS-VR group. The animals were anethestizod with ketamine 15 mg/kg, diazepam 1.5 mg/kg and atropine 0.01 mg/kg. Femoral artery and vein were cannulatod for MAP mornitoring, blood-letting, blood sampling and fluid infusion. Hemorrhagic shock (HS) was induced according to the method described by Wiggers and Ingraham. If MAP was reduced to 35-45 mm Hg and maintained for 90 min, the establishment of HS was considered successful. The animals were then resuscitated for 60 min with blood transfusion and infusion of lactated Ringer's solution (equal to the volume of blood loss). MAP, HR, CVP, PAP, PCWP and CO were monitored and recorded before blood-letting (T0, baseline), after successful establishment of HS model (T1), and immediately (T2) and at 30 min (T3), 60 min (T4), 120 min (T5) and 240 min (T6) after the end of resuscitation. Blood samples were obtained at the above time points for determination of concentrations of plasma ET, NO, BUN and Cr. The ET/NO ratio was calculated. The linear correlation was analyzed between plasma ET/NO ratio and the concentrations of BUN and Cr. Results MAP, PAP, CVP and CO were significantly lower, and HR, concentrations of plasma ET, BUN and Cr higher and ET/NO ratio at T1 higher,PAP and CVP at T2 higher, HR at T4 lower, PAP and ET/NO ratio at T6 lower and plasma NO concentration at T4-6 higher in group HS-VR than in group S (P<0.05 or 0.01). The plasma ET/NO ratio was positively correlated with the concentrations of BUN and Cr (r=0.366, 0.445, P<0.01). Conclusion Volume resuscitntion can improve renal function through correcting the imbalance of ET and NO in pigs with hemorrhagic shock. Key words: Shock, hemorrhagic; Resuscitation; Endothelins; Nitric oxide; Kidney function tests

Changes of Endothelin and Calcitonin Gene-related Peptide Concentrations in Plasma During Propofol Anesthesia

We had previously reported that plasma concentrations of endothelin (ET) decreased significantly in the operating room during desflurane anesthesia. The purpose of the present study was to explore whether changes in plasma ET and calcitonin gene-related peptide (CGRP) concentrations were altered during propofol anesthesia in patients undergoing clipping of an intracranial aneurysm. Forty-five patients scheduled for selective craniotomy and aneurysm clipping were anesthetized with propofol. A catheter was inserted into the radial artery for blood sampling before anesthesia. Serial plasma concentrations of ET and CGRP were determined before induction, after dura incision, after clipping of the aneurysm, and 30 minutes after clipping. ET concentrations in the plasma increased significantly after clipping of the aneurysm compared with concentrations after dura incision. However, no significant changes in ET levels were found after anesthesia. Plasma concentrations of CGRP decreased significantly during anesthesia. This evidence suggests that direct stimulation of the intracalvarium blood vessel before aneurysm clipping may increase ET; however, propofol did not decrease ET, in contrast with our previously reported findings for desflurane anesthesia. Considering the well-recognized vasodilatory effect of CGRP, it is possible that a decrease in the plasma concentration of CGRP plays a role in the pathogenesis of cerebral vasospasm, which is often seen postoperatively.

UPREGULATED ENDOTHELIN SYSTEM IN DIABETIC VASCULAR DYSFUNCTION AND EARLY RETINOPATHY IS REVERSED BY CPU0213 AND TOTAL TRITERPENE ACIDS FROM FRUCTUS CORNI

1. The aims of the present study were to examine whether: (i) upregulation of the endothelin (ET) pathway is involved in impairment of vascular relaxation and early retinopathy in diabetic rats; and (ii) vascular and retinal abnormalities respond to the total triterpene acid (TTA) isolated from Fructus Corni compared with responses to the novel endothelin receptor antagonist CPU0213 and aminoguanidine (AMG), a special antagonist for advanced glycation end-products (AGE) and inducible nitric oxide synthase (iNOS). 2. Male Sprague-Dawley rats were randomized into five groups, namely a normal control and four diabetic groups, which included an untreated diabetic group and groups treated with AMG (100 mg/kg, i.g.), CPU0213 (30 mg/kg, s.c.) or TTA (50 mg/kg, i.g.). Diabetes was induced by single injection of streptozotocin (60 mg/kg, i.p.) on the 1st day. The mRNA expression of prepro-endothelin-1 (ppET-1), endothelin-converting enzyme (ECE) and iNOS in the thoracic aorta and mRNA for ET(A) receptors and iNOS in the retina were detected by reverse transcription-polymerase chain reaction. Vasorelaxation to acetylcholine (ACh) and functional assessment of nitric oxide (NO) bioavailability was determined in the thoracic aorta. 3. We observed upregulated mRNA expression of iNOS, ppET-1 and ECE in the thoracic aorta and upregulated mRNA for the ET(A) receptor and iNOS in the retina in the untreated diabetic group. Vasodilatation mediated by ACh and NO bioavailability were markedly reduced in the thoracic aorta compared with the normal control group. These abnormalities were essentially reversed by TTA, CPU0213 or AMG, with the exception with that AMG did not modify vasodilatation to ACh. 4. These data suggest that upregulation of gene transcription of the ET system mediates depressed vasorelaxation, NO bioavailability and changes in iNOS and ET(A) receptors that reflect early retinopathy in diabetic rats. Total triterpene acid, in terms of pharmacological properties resembling the endothelin receptor antagonist CPU0213, is effective in normalizing expression of the ET system and iNOS in early diabetic retinopathy and vasculaopathy.

Effects of alcohol withdrawal on blood pressure in hypertensive heavy drinkers

Epidemiological investigations have demonstrated a close association between heavy alcohol consumption and hypertension. The mechanisms of this association, however, remain elusive. We studied the effects of alcohol withdrawal on blood pressure, hormonal parameters, and circulating markers of endothelial activity. In 14 hypertensive heavy alcohol consumers (> 200 g/day) who agreed to participate in a hospital withdrawal programme we monitored, for 30 days, blood pressure, plasma levels of renin, aldosterone, cortisol, endothelin, and plasminogen activator inhibitor 1 (PAI-1), and urinary levels of catecholamines. Patients in the withdrawal group were compared with eight hypertensive heavy drinkers who refused to participate in the programme and maintained regular alcohol consumption and 11 normotensive teetotalers. By the third day after withdrawal, blood pressure was significantly decreased and the normalization of levels was obtained in 13 of 14 patients by the end of the study. Alcohol withdrawal significantly decreased plasma aldosterone and cortisol levels, but did not affect levels of active renin and fractionated urinary catecholamines. At baseline, plasma endothelin and PAI-1 levels were significantly higher in alcoholic individuals than in teetotalers, and after the cessation of alcohol intake decreased progressively, reaching levels different from baseline within 1 week. A significant correlation was found between changes in endothelin and PAI-1, and blood pressure variations during alcohol abstinence that remained significant only for endothelin with the multivariate approach. Hypertension is rapidly reversible in the majority of heavy drinkers after the withdrawal of alcohol consumption. In these patients, hypertension is associated with an increased release of endothelial factors that might contribute to the increase in blood pressure.

Endothelin Receptor Remodeling Induces the Portal Venous Hyper-Response to Endothelin Following Endotoxin Pretreatment

The purpose of this study was to determine the changes in endothelin (ET) receptor subtype expression and their functional significance after endotoxin pretreatment. Rats were pretreated with lipopolysaccharide (LPS) or sterile saline (control). After 24 h, liver samples were homogenized and competitive receptor binding assays were performed. There was no significant difference in ET receptor binding affinity between the control and LPS groups. However, the receptor subtype density showed a significant increase in ET(B) receptors in LPS-treated rats, whereas the amount of ET(A) receptors was almost identical between the two groups. In control, almost all ET receptors (95%) were displaced by using combined ET(A) antagonist (BQ-610) and ET(B) agonist (IRL-1620) as competitors, whereas only 80% (P < 0.05 versus control) was displaced in LPS group, raising the possibility of novel type of ET receptor expression. An infusion of ET(B) agonist (Sarafotoxin 6c, S6c) through portal vein in isolated perfused livers produced the same pressure response in both LPS and control groups; however, the portal pressure increase in response to the ET-1, which binds all ET receptors, was significantly potentiated in LPS-treated rats compared to controls. We conclude that altered regulation of ET receptors, in particular, the appearance of ET binding capacity that is not displaced by ET(A) or ET(B) competitors, may explain the hyper-response of the portal venous system to ET-1 during endotoxemia.

Endothelin and Endothelin A/B Receptors Are Increased after Ischaemic Acute Renal Failure

Background/Aims: Endothelin (ET) has been implicated as an indirect mediator of injury following acute renal ischaemia (ARI). The purpose of this study was to localize and quantitate ET and ET_A and ET_B receptors following ARI. Methods: A model of ARI, well characterized previously, was produced by 45 min occlusion of the renal pedicle of unilaterally nephrectomized female Sprague-Dawley rats. Animals were sacrificed 1, 2, 4, 8, 16, 32 and 64 days after ischaemia (n = 6). Corresponding control groups with unilateral nephrectomy but no ischaemia were sacrificed after 0, 8 and 64 days. Immunohistochemistry for ET-1, -2 and -3 was performed. Tissue ET levels were calculated by RIA (femtomoles per kidney). Receptor ligand binding studies for ET_A and ET_B receptors were performed by autoradiography on frozen kidney sections and quantitated by densitometry (relative optical density per square millimetre). Results: The concentration of tissue ET increased from 24 h after ischaemia and remained significantly increased for the duration of the study, reaching a maximum at 8 days. There was a small increase in the non-ischaemic 8-day control group, but this returned to basal levels by day 64. The increase in tissue ET 8 days after ischaemia was localized by immunohistochemistry to renal medullary interstitial cells, damaged tubules at the corticomedullary junction and peritubular capillaries surrounding these damaged tubules. Increases in cortical ET_A and ET_B receptors were evident 24 h after ischaemia and were maximal 8 days after ischaemia, before returning to basal levels at 16 days. After a small increase 24 h after ischaemia, medullary ET_A receptors decreased on day 4 before returning to basal levels on day 8 after ischaemia. Medullary ET_B receptors, however, decreased on day 4 after ischaemia and remained low throughout the duration of the study. Conclusion: The previously reported amelioration of pathological changes resulting from the use of ET receptor antagonists after ARI may be related to the quantitative and qualitative changes in tissue ET and ET receptors observed in this study.

Subarachnoid hemorrhage induced sympathoexcitation arises due to changes in endothelin and/or nitric oxide activity

The demonstration of the effectiveness of endothelin antagonists and nitric oxide donors in managing vasospasm following subarachnoid hemorrhage is encouraging. Whether such drugs can modify the sympathoexcitation that accompanies this condition remains unknown and was the basis for the present report. Subarachnoid hemorrhage was induced in conscious rats by injecting blood via a catheter placed along the surface of the brain and directed towards the circle of Willis. We combined measurements of arterial plasma catecholamines with the spectral analysis of blood pressure variability in order to examine sympathetic nervous activation following subarachnoid hemorrhage. Experiments were performed in untreated animals and in rats following pretreatment with either bosentan or sodium nitroprusside. Indicative of a pronounced sympathoexcitation, the 0.2-0.6 Hz frequency components of blood pressure were markedly elevated following subarachnoid hemorrhage (2.5 +/- 0.5 vs. 8.9 +/- 2.6 mmHg2, P < 0.01). Parallel changes in plasma norepinephrine concentration were observed (1.0 +/- 0.2 vs. 2.4 +/- 0.4 nmol/l, P < 0.01). The subarachnoid injection of saline did not modify blood pressure variability or plasma norepinephrine concentrations. Pretreatment with either bosentan or sodium nitroprusside completely prevented the subarachnoid hemorrhage induced sympathoexcitation. Experimental subarachnoid hemorrhage is associated with a pronounced activation of the sympathetic nervous system. It would appear that this sympathoexcitation has its roots ensconced in either the release of endothelin or an impairment in nitric oxide mediated vasodilation.

Involvement of glial endothelin/nitric oxide in delayed neuronal death of rat hippocampus after transient forebrain ischemia.

1. We examined time- and cell-type-dependent changes in endothelin (ET)-1-like immunoreactivity, ET receptors binding and nitric oxide (NO) synthase (NOS) activity in CA1 subfields of the hippocampus of stroke-prone spontaneously hypertensive rats subjected to a 10-min bilateral carotid occlusion and reperfusion. 2. Microglia aggregated in accord with neuronal death and expressed a high density of ET(B) receptors and an intense NOS activity in the damaged CA1 pyramidal cell layer, 7 days after the induced transient forebrain ischemia. The increased NOS activity and ET(B) receptor in microglia disappeared 28 days after this transient ischemia. 3. In contrast to microglia, astrocytes presented a moderate level of ET-1-like immunoreactivity, ET(B) receptors, and NOS activity in all areas of the damaged CA1 subfields, 7 days after the ischemia. These events were further enhanced 28 days after the ischemia. 4. In light of these findings, the possibility that the microglial and the astrocytic ET(B)/NO system largely contributes to development of the neuronal death and to reconstitution of the damaged neuronal tissue, respectively, in the hippocampus subjected to a transient forebrain ischemia would have to be considered.

Gestational changes in endothelin-1-induced receptors and myometrial contractions in rat.

The present experiments were performed to characterize the gestational changes in endothelin (ET)-1-induced myometrial contractions and ET receptors in rat. ET-1-induced contractions were composed of two types: increases in resting tone and rhythmic contractions. The increase in resting tone was decreased at 7 days of gestation, but increased at 20 days. The increase in amplitude and frequency of rhythmic contractions remained unchanged during days 7-14 of gestation. Continuous rhythmic contractions were not produced by ET-1 near the term. Both contractions were inhibited by the antagonists BQ 123 and Ro 46-2005 but not by RES 701-1 or BQ 788. In binding studies, total binding sites of [1251]-ET-1 were unchanged, however higher affinity binding sites appeared during pregnancy in addition to the lower affinity sites. The specific [125I]-ET-1 binding in non-pregnant and pregnant myometrium was completely inhibited by unlabelled ET-1 and Ro 46-2005. In contrast, the proportion which was inhibited by BQ 123 was decreased during pregnancy. In conclusion, characteristic gestational changes were the augmentation of ET-1-induced increased resting tone near term, and the appearance of high affinity ET-1 binding sites and an increase in BQ 123-resistant ET-1 binding sites during pregnancy. Further investigations are needed to understand the physiological role of these changes.

Superoxide-induced changes in endothelin (ET) receptors in hepatic stellate cells

Background/Aims: Reactive oxygen species are mediators of various pathophysiologic events, including postischemic reperfusion injury and inflammation. Generation of reactive oxygen species and consequent organ injury are associated with increased levels of a powerful vasoconstrictor peptide endothelin-1. Current evidence suggests that actions of endothelin-1 on the contractile and fibrogenic transdifferentiated stellate cells may play a critical role in hepatic pathophysiology. the aim of this investigation was to determine whether reactive oxygen species modulate the synthesis of endothelin-1 and its receptors in stellate cells. Methods: Primary cultures of transdifferentiated stellate cells were exposed to reactive oxygen species-generating system, hypoxanthine/xanthine oxidase, before determination of endothelin-1 and its receptors. Results: The treatment caused an initial decrease in ET-1 receptor density (about 30% at 30 min), followed by a significant increase over the basal level at 6 h. The increase in the receptors, which occurred specifically in the ET B subtype, progressed thereafter up to 24 h and was accompanied by an augmented functional response, as indicated by an enhanced endothelin-1-induced release of [ 3H]arachidonic acid from the prelabeled cells. Furthermore, treatment of cells for 24 h but not 30 min caused increased expression of ET B mRNA as determined by semi-quantitative polymerase chain reaction. The release of endothelin-1 in the culture medium was also enhanced by hypoxanthine/xanthine oxidase treatment. These effects of hypoxanthine/xanthine oxidase were inhibited by superoxide dismutase and dimethyl sulfoxide. ET-1-induced [ 3H]arachidonic acid release was also inhibited by the ET B receptor antagonist BQ788, but not by the ET A receptor antagonist BQ123. Conclusions: These findings indicate that interactions between ET-1 and stellate cells during episodes of the generation of reactive oxygen species can be an important mechanism in the pathophysiology of hepatic disorders.