Regional distribution of endothelin-1 and endothelin converting enzyme-1 in porcine endotoxemia.

Endothelin-1 (ET-1) levels are markedly increased in sepsis. Since ET-1 is primarily transcriptionally regulated, there should be a corresponding increase in pre-pro-endothelin-1 (ppET-1). Our objective was to determine whether ppET-1 is increased in pigs with a low systemic vascular resistance. We also examined the distribution of ET-1 and the regulation of endothelin-converting enzyme 1 (ECE-1), the rate limiting enzyme in ET-1 production. We anesthetized and ventilated 16 pigs. We measured arterial, pulmonary, and central venous pressures, as well as cardiac output. ET-1 was measured by radioimmunoassay in plasma and in multiple tissues. We infused 20 microg/kg of endotoxin over 2 h and then sacrificed the animals. ppET-1 and ECE-1 mRNA were assessed by Northern analysis. We performed immunohistochemistry for the assessment of tissue ET-1 and ECE-1. The systemic vascular resistance rose at 30 min, but fell by 120 min. Plasma ET-1 more than doubled by 2 h. However, there was no change in the concentration of ET-1 in any tissue except in the pulmonary artery. By immunohistochemistry, there was also no change in ET-1 in aorta, vena cava, heart, lung, liver, and kidney. Distribution of ECE-1 followed that of ET-1 on immunohistochemistry. There was a significant increase in ppET-1 mRNA in liver, kidney papillae, and vena cava, and a tendency for an increase in other tissues. This was paralleled by an increase in ECE-1 mRNA. In conclusion, the amount of ECE-1 mRNA and protein parallel those of ET-1. Endotoxemia is associated with a marked increase in plasma ET-1 and an increase in ppET-1 and ECE-1 mRNA in multiple tissues; however, there was no significant change in tissue ET-1 except in the pulmonary artery. The rise in plasma levels without a change in tissue levels suggests a greater release into the vasculature in sepsis than under normal conditions.

Effect of endothelin receptor antagonist on lung allograft apoptosis and NOSII expression.

BACKGROUND: It is postulated that apoptosis contributes to ischemia-reperfusion graft dysfunction after lung transplantation. The purpose of this study was to determine whether the improvement in lung function that we previously observed with the use of an endothelin-1 (ET-1) receptor antagonist after ischemia-reperfusion injury is associated with a reduction in inducible nitric oxide synthase (NOSII) expression and programmed cell death. METHODS: Left lung canine allotransplantation was performed. Harvested lung blocks were preserved with modified Eurocollins solution and stored at 4 degrees C for 18 to 20 hours. Lung allografts were tested for the expression of NOSII by immunohistochemistry, and extent of apoptosis by terminal dUTP nick end-labeling (TUNEL). Animals blindly received either an intravenous infusion of saline (control) or the ET-1 receptor antagonist (SB209670) (15 microg/kg/min). Infusion began 30 minutes pretransplantation and continued to 6 hours posttransplantation. RESULTS: Immunohistochemical analysis demonstrated significantly stronger NOSII immunostaining in the allografts of the saline control group (36.5%+/-3.6%) compared with native right lungs (6.9%+/-1.3%, p < 0.001) or the ET-receptor antagonist treatment group (9.6%+/-1.4%, p < 0.001). The TUNEL staining revealed a significantly stronger labeling in the allografts of the saline treatment control group (40.7%+/-6.2%) compared with native right lungs (5.0%+/-0.6%, p < 0.005) or the ET receptor antagonist treatment group (14.1%+/-2.8%, p < 0.01). CONCLUSIONS: We conclude that treatment of lung allografts with the ET-1 receptor antagonist SB209670 reduces the area of NOSII expression and the extent of apoptosis, factors known to contribute to the process of prolonged ischemia-reperfusion injury.

Nitric oxide system in needle-induced transmyocardial revascularization.

BACKGROUND: Nitric oxide (NO) promotes endothelial proliferation and migration, essential for angiogenesis. The purpose of this study was to determine the cellular expression of inducible and endothelial nitric oxide synthases (iNOS and eNOS) in an ischemic cardiomyopathy animal model of needle-induced transmyocardial revascularization (TMR). METHODS: Myocardial infarction was created in rats by ligating the left coronary artery, and animals were divided into two groups: no-TMR group (served as control) and TMR group (underwent concomitant TMR by the creation of six transmural channels with a 25-gauge needle in the ischemic area). Rats were sacrificed at intervals of 1, 2, 4, and 8 weeks. Immunohistochemistry using specific antisera was performed for iNOS, eNOS, and endothelial cell marker factor VIII. Vascular density and positive staining area with either iNOS or eNOS were assessed in the infarcted myocardium. RESULTS: Vascular density in the infarcted myocardium was significantly increased in the TMR group (p < 0.001). The positive staining area for iNOS and the intensity of iNOS immunoreactivity in cardiomyocytes, vascular endothelium, and macrophages were significantly greater in the TMR group (p < 0.05). However, these differences were seen only in the first 2 weeks after TMR. There was no significant difference in the expression of eNOS between groups. CONCLUSIONS: A mechanical injury using needle puncture in an ischemic myocardium increased vascular density and is associated with increased expression of myocardial iNOS. Increased production of NO derived from iNOS may contribute to the angiogenic response of TMR.

Successful retrieval and function of lungs from non-heart-beating donors.

BACKGROUND: Lung transplantation has been used effectively as a therapeutic tool in end-stage pulmonary diseases, but organ shortages have restricted its use. There is growing interest in alternative organ sources such as organs from circulation-arrested cadavers, so called non-heart-beating donors. METHODS: We examined the effects of postmortem rapid in situ cadaver lung cooling by bilateral chest cavity flushing (group 2) and by pulmonary artery flush through right heart catheterization followed by pleural cavity flushing (group 3) on pulmonary function and morphology in a rabbit non-heart-beating donor model. The results were compared with those in a control group of heart-beating donors (group 1). RESULTS: At the end of a 2-hour reperfusion period, there were no significant differences in mean pulmonary artery pressure, pulmonary vascular resistance, pulmonary compliance, arteriovenous oxygen, pulmonary wet to dry weight ratio, and lung morphology between the three groups. CONCLUSIONS: Our study demonstrates that using bilateral chest cavity flushing with or without pulmonary flush protects the function and morphology of cadaver lungs and renders them suitable for lung transplantation.

Endothelin receptor antagonist SB209670 decreases lung allograft apoptosis and improves lung graft function after prolonged ischemia.

Apoptosis has been postulated as a contributing factor in ischemia-reperfusion graft dysfunction following lung transplantation. The purpose of this study was to determine whether treatment with an endothelin-A/endothelin-B- (ET(A)/ET(B)) receptor antagonist could reduce the level of apoptosis observed in the lung following ischemia-reperfusion injury. Eleven dogs were subjected to left lung allotransplantation. Heart-lung blocks were harvested from donor dogs and preserved with modified Eurocollins solution and stored at 4 degrees C for 18 to 20 h. We investigated the level of apoptosis by terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL), in the lungs of animals receiving an intravenous infusion of saline (control, n = 5) or the ET receptor antagonist SB209670 (n = 6) (15 microg/kg/min). The infusion began 30 min prior to transplantation and continued for up to 6 h thereafter. The TUNEL staining was significantly higher in the airway epithelium and the parenchyma of the saline (control) group (40.67 +/- 6.16), compared with native right lungs (5.00 +/- 0.56) and the treatment group (14.13 +/- 2.84). We conclude that treatment of lung allografts with the mixed ET(A)/ET(B)-receptor antagonist SB209670 can ameliorate lung injury by reducing the level of apoptosis seen in the allograft following ischemia-reperfusion injury.

An automated interrupted suturing device for coronary artery bypass grafting: automated coronary anastomosis.

BACKGROUND: The purpose of this study was to have a preliminary assessment of the safety and efficacy of an automated vascular suturing device. METHODS: The device (Heartflo, Perclose/Abbott Labs, Redwood City, CA), which delivers 10 interrupted 7-0 polypropylene sutures between side-to-side arteriotomies, was evaluated in animals (8 Yorkshire pigs). RESULTS: Tissue edge capture and quality of anastomosis were highly rated. Time of anastomoses averaged 22 minutes. This time was prolonged primarily due to suture management, tying of interrupted sutures, and learning curve effects. Six of the anastomoses were hemostatic and two required an additional stitch each. Angiography and histology of the anastomosis confirmed patency and quality of the anastomosis. CONCLUSIONS: Our preliminary results indicate that the Heartflo automated anastomotic device is safe and effective. Preclinical and clinical studies to validate its acute and long-term effectiveness will commence shortly.

Inhibition of cyclooxygenase-2 improves cardiac function in myocardial infarction.

Induction of cyclooxygenase-2 (COX-2) in ischemic myocardium is thought to increase the production of proinflammatory prostanoids and contribute significantly to the ischemic inflammation. Left ventricular myocardial infarction (MI) was created by ligating the left coronary artery in Lewis rats. Hemodynamic measurements at 4 weeks showed better cardiac function in the group treated with a selective COX-2 inhibitor (DFU; 5 mg/kg/day) for 2 weeks after induction of MI compared to the vehicle treated group. These results suggest that induction of COX-2 contributes to myocardial dysfunction, and that selective inhibition of COX-2 could constitute an important therapeutic target for the treatment of MI.

Prostaglandin H synthase 2 expression in airway cells from patients with asthma and chronic obstructive pulmonary disease.

Products of the prostaglandin H synthase (PGHS) metabolic pathway are thought to play a role in the pathogenesis of asthma. We determined the level of expression of the constitutive (PGHS-1) and inducible (PGHS-2) isoforms of the enzyme in induced sputum and bronchial biopsies of patients with asthma, patients with chronic obstructive pulmonary disease (COPD), and unaffected control subjects by immunocyto- and immunohistochemistry. Immunoreactivity for PGHS-2 was significantly greater in the induced sputum of patients with asthma and patients with COPD compared with unaffected control subjects. The level of PGHS-2 was greater in asthma than in COPD. Immunoreactivity for PGHS-1 increased in cells in the induced sputum of patients with asthma and patients with COPD compared with that of unaffected control subjects. Immunostained cells included macrophages, eosinophils, and neutrophils. Greater PGHS-2 immunoreactivity was seen in the submucosal inflammatory infiltrate and in the airway epithelium of patients with asthma compared with unaffected control subjects. In summary, we demonstrate an induction of PGHS-2 in asthma, suggesting increased formation of prostanoids, which may contribute to the inflammatory process.

Chemokine- and cytokine-induced expression of endothelin 1 and endothelin-converting enzyme 1 in endothelial cells.

BACKGROUND: Endothelin 1 (ET-1) is a product of endothelial and many other cell types that possesses a wide range of actions, including vasoconstriction, bronchoconstriction, and mitogenic activity on smooth muscle cells and fibroblasts. ET-1 release and expression is induced in several disease conditions associated with inflammation and cellular injury. OBJECTIVE: The purpose of this study is to determine the effects of alpha-chemokines (IL-8 and melanoma growth-stimulating activator), beta-chemokines (monocyte chemotactic protein 1, macrophage inflammatory protein 1alpha [MIP-1alpha], MIP-1beta, and RANTES), and proinflammatory cytokines (IL-1beta, TNF-alpha, and IFN-gamma) on the expression of both ET-1 and endothelin-converting enzyme 1 (ECE-1) by human umbilical vein endothelial cells. METHODS: Subconfluent monolayers of human umbilical vein endothelial cells were incubated with each chemokine individually for 24 hours or with a mixture (cytomix) of TNF-alpha, IL-1beta, and IFN-gamma for 6 and 24 hours. RESULTS: Incubation with the alpha-chemokines melanoma growth-stimulating activity and IL-8 did not significantly increase ET-1 and ECE-1 messenger (m)RNA expression and had no effect on ET-1 release. Monocyte chemotactic protein 1 exerted the most potent increase in ET-1 and ECE-1 mRNA and ET-1 release among all chemokines studied (P <.05). MIP-1alpha and RANTES exerted a moderate, but significant, increase on the ET system (P <.05). The cytomix resulted in a significant increase in ET-1 and ECE-1 mRNA expression (P <.05). CONCLUSION: These data demonstrate that, like cytokines, chemokines can induce endothelial ET-1 and ECE-1 in vitro and suggest a possible role for these inflammatory mediators in the induction of the ET system in inflammatory and vascular diseases.

Endothelin and cardiac transplantation.

Endothelins are 21 amino acid peptides that are produced ubiquitously by vascular endothelial cells, smooth muscle cells, and other cells in different organs. Endothelins are secreted as big-endothelins that are converted to active proteins by the endothelin-converting enzyme. These peptides possess many biological activities, such as vasoconstriction and mitogenesis, and are involved in numerous physiological and pathophysiological processes in humans. Elevated plasma levels of endothelin have been associated with heart failure, and increased immunoreactivity for endothelin is observed in transplant coronary artery disease. In this brief review, we will discuss the regulation of endothelin in cardiac transplantation and the pathological role this peptide plays in renal impairment, systemic hypertension, graft rejection and arteriosclerosis after heart transplantation.

Angiogenic response induced by mechanical transmyocardial revascularization.

BACKGROUND: Angiogenesis is the proposed mechanism of transmyocardial revascularization. We evaluated mechanical transmyocardial revascularization in a chronically ischemic porcine model by measuring myocardial angiogenic response. METHODS: Ameroid constrictors were implanted 6 weeks before mechanical transmyocardial revascularization. Group I (n = 5) and group II (n = 3) animals received 30 punctures with an 18-gauge needle and samples were harvested at 1 and 4 weeks, respectively, after the operation. Group III (n = 5) had sternotomy only and served as the control group. Myocardial samples were immunohistochemically stained for vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF), and transforming growth factor beta (TGF-beta) using specific antibodies. Growth factor expression was quantified by means of computer-assisted morphometry. Vascular density was assessed by immunohistochemical stain for VEGF and factor VIII. RESULTS: Compared with group III, increased angiogenic factor levels were found in group I (VEGF 0.47 +/- 0.03 mm(2) vs 0.05 +/- 0.05 mm(2), P =.000; bFGF 0.67 +/- 0.14 mm(2) vs 0.03 +/- 0.03 mm(2), P =. 000; TGF-beta 1.40 +/- 0.18 mm(2) vs 0.09 +/- 0.06 mm(2), P = 0.000), and in group II (VEGF 0.34 +/- 0.06 mm(2) vs 0.05 +/- 0.05 mm(2), P =.003; bFGF 0.06 +/- 0.02 mm(2) vs 0.03 +/- 0.03 mm(2), P =.135; TGF-beta 0.28 +/- 0.09 mm(2) vs 0.09 +/- 0.06 mm(2), P =.042). Vascular densities after mechanical transmyocardial revascularization were also increased (group I, VEGF stain 8.1 +/- 0. 6 vs 1.1 +/- 0.5, P =.000; factor VIII stain 5.1 +/- 2.7 vs 0.4 +/- 0.3, P =.018; group II, VEGF stain 1.9 +/- 0.5 vs 1.1 +/- 0.5, P = 0. 107; factor VIII stain 2.3 +/- 0.4 vs 0.4 +/- 0.3, P =.004). CONCLUSIONS: Mechanical transmyocardial revascularization is associated with increased angiogenic factor expression and concomitant neovascularization at up to 4 weeks. These changes are indistinguishable from those of laser transmyocardial revascularization. Myocardial perfusion studies are needed to establish the functional significance of these angiogenic changes.

Thoracic Surgery Directors Association Award. Angiogenesis in transmyocardial revascularization: comparison of laser versus mechanical punctures.

BACKGROUND: Transmyocardial laser revascularization (TMLR), which has been shown to reduce angina in clinical trials, was originally based on the belief that laser channels are unique and can remain patent. An increasing body of evidence indicates otherwise, and transmyocardial revascularization (TMR) angiogenesis is currently thought to be induced by nonspecific inflammatory response to tissue injuries. We tested the hypothesis that mechanical transmyocardial revascularization (TMMR) may induce angiogenic responses similar to that seen with lasers. METHODS: Ameroid constrictors were implanted around proximal circumflex arteries of porcine hearts. Six weeks later, they were randomly assigned (n = 5 each) to receive 10 transmural channels in the ischemic zone by a carbon dioxide laser (group I) or by a needle (group II). A third group (group III) had 30 needle channels in the same area, while a control group (group IV) received no TMR. The hearts were harvested 1 week later, and, using immunohistochemistry, vascular endothelial growth factor (VEGF) expression was studied and quantified by computerized morphometric analysis. Densities of vascular structures positively stained for VEGF per high-power field (HPF) were also compared. RESULTS: Virtually no TMR channels remained patent histologically. Group III had a significant higher level of total VEGF expression (14.18+/-0.78 mm2) compared with group I (7.07+/-2.06 mm2, p < 0.001) and group II (4.74+/-3.35 mm2, p < 0.001). Vascular density was significantly elevated in all treatment groups compared with the control (group I, 7.7+/-0.8/HPF vs group II, 4.5+/-2.3/HPF vs group III, 8.1+/-0.6/HPF vs group IV, 1.1+/-0.5/HPF). CONCLUSIONS: In view of the significant cost implications, our findings that needle punctures may also induce angiogenic response comparable with that with laser suggest that it is justifiable and desirable to include a TMMR arm for comparison with TMLR in future clinical trials.

Immunolocalization of cyclooxygenase-2 in the macula densa of human elderly.

To gain insight into the role of prostanoids in human kidney function, we examined the distribution of cyclooxygenase (COX) 1 and COX-2 by immunofluorescence and immunohistochemistry in human kidneys from adults of various age groups. COX-1 was detected in the collecting ducts, thin loops of Henle and portions of the renal vasculature. COX-2 was detected in the renal vasculature, medullary interstitial cells, and the macula densa. In addition, COX-2 immunoreactivity was noted in afferent arteries and the macula densa of the renal cortex and was more evident in the kidneys of older adults.

Endothelial expression of endothelial nitric oxide synthase and endothelin-1 in human coronary artery disease. Specific reference to underlying lesion.

Nitric oxide and endothelin-1 (ET-1) are two major endothelium-derived factors with opposing effects on the function and structure of the vessel wall. We investigated the endothelial expression of endothelial nitric oxide synthase (eNOS) and ET-1 in coronary artery disease (CAD) with special reference to the types of underlying lesions. Immunohistochemistry and in situ hybridization were performed in coronary arteries of heart transplant recipients with (n = 16) and without (n = 11) CAD. All coronary arteries from patients with CAD (n = 23) had concentric fibrous or advanced lesions, whereas most of the arteries (25 of 31) from patients with non-CAD showed normal appearance (myointimal thickening only) or eccentric lesions alone. Normal coronary segments consistently showed apparent endothelial immunoreactivity and mRNA signals for both eNOS and ET-1. In atherosclerotic coronary segments, endothelial expression of eNOS and ET-1 was reduced in most lesion sites, particularly in severe subendothelial lesions with dense fibrosis or macrophage accumulation, but not with smooth muscle cells only. Conversely apparent ET-1, compared with weak or focal eNOS signals, were more frequently seen in coronary segments with concentric severe lesions from CAD but not non-CAD patients. Immunoreactivity and mRNA signals for ET-1 were co-localized with those for ET converting enzyme-1 in the endothelium, as well as in the underlying macrophages and smooth muscle cells. These results indicate the presence of differential endothelial expression of eNOS and ET-1 in diseased human coronary arteries with severe concentric atherosclerotic lesions, a finding that was rare in atherosclerotic lesions of coronary arteries of non-CAD patients. Altered expression of endothelium-derived factors may contribute to abnormality of coronary vasomotor tone and the formation of subendothelial lesions in CAD.

Cyclooxygenase-2 and nuclear factor-kappaB in myocardium of end stage human heart failure.

Over the past three decades, numerous studies have shown diverse functional and morphological effects for prostanoids on cardiac myocytes with levels of prostanoids elevated in congestive heart failure. We examined the expression of cyclooxygenase-2 (COX-2) and activation of nuclear factor-kappaB (NF-kappaB) in failing human hearts. Expression of COX-2 and activation of NF-kappaB were examined in myocardial tissues from 27 patients with end stage heart failure, 2 septic patients, and 8 normal control subjects. There was little or no expression of COX-2 and NF-kappaB in the control hearts. There was abundant expression of COX-2 mRNA and protein in myocytes and inflammatory cells in areas of fibrotic scar compared with regions of normal morphology in all cases of heart failure, except in the cases with sepsis which showed abundant COX-2 throughout the myocardium. Sites of NF-kappaB activation were associated with those of COX-2 expression. We concluded that COX-2 expression and NF-kappaB activation are elevated in patients with congestive heart failure. Cellular induction of both molecules is associated with sites of inflammation and scar formation. (c)1999 by CHF, Inc.

Pulmonary injury in recipients of discordant hepatic and renal xenografts in the dog-to-pig model.

Work in our lab demonstrated that the early post-operative course of discordant hepatic and renal xenotransplantation is complicated by a pulmonary injury. The aim of this study was to characterize the nature of this injury, as well as to determine whether endothelin-1 (ET-1) and inducible-nitric oxide synthase (iNOS) are present in this form of pulmonary injury. Dog-to-pig orthotopic liver and kidney xenografts were performed. Pulmonary artery pressures were monitored throughout all procedures. The lungs were stained with monoclonal antibodies for ET-1, endothelin converting enzyme-1, and iNOS. The lungs from pig recipients of hepatic or renal xenografts were compared to lungs from untreated pigs. Pulmonary artery pressures were elevated in recipients of liver xenografts when the suprahepatic caval cross clamp was placed and continued to rise to systolic levels following unclamping. The mean pulmonary artery pressures in recipients of renal and hepatic xenografts rose significantly following revascularization. Pathology in lungs from kidney and liver recipients was similar, showing congestion with peribronchial and septal edema, with diffuse adhesion of PMN to alveolar endothelium. ET-1, endothelin converting enzyme-1 (ECE-1), and iNOS staining was widespread and intense in alveolar and pulmonary arterial endothelium. Discordant xenotransplantation of livers and kidneys is associated with a significant early pulmonary injury that is associated with early PMN infiltration and expression of ET-1 and iNOS.

Pulmonary and cardiac expression of preproendothelin-1 mRNA are increased in heart failure after myocardial infarction in rats. Localization of preproendothelin-1 mRNA and endothelin peptide.

OBJECTIVES: Recent reports indicate that endothelin (ET) plays an important pathophysiological role in congestive heart failure (CHF). However, existing data on local cardiopulmonary ET production are few. No studies have hitherto examined the specific anatomic localization of cardiopulmonary ET synthesis in CHF. Thus, the aims of the present study were to examine whether cardiopulmonary preproET-1 mRNA synthesis is upregulated in CHF and to determine the anatomic localization of preproET-1 mRNA and the mature peptide. METHODS: CHF was induced in rats by occluding the left coronary artery. Only animals with a left ventricular end-diastolic pressure above 15 mmHg after one week were included (n = 28). Sham-operated animals served as controls (n = 24). Hearts and lungs were examined by mRNA slot blot analyses, in situ hybridization (ISH) and immunohistochemistry (IHC). RESULTS: In CHF-rats, slot blot analyses revealed a 3.5 +/- 1.1-fold and a 6.4 +/- 0.8-fold upregulation of preproET-1 mRNA in the noninfarcted and the infarcted area of the left ventricles, respectively (p < 0.05 for both). ISH revealed that the preproET-1 mRNA was localized predominantly over the granulation tissue in the infarcted region. The ET peptide was predominantly localized to inflammatory cells and remaining cardiomyocytes in the infarcted region as determined by IHC. Lungs from CHF-rats showed a 1.5 +/- 0.1-fold upregulation of preproET-1 mRNA (p = 0.01). The most abundant preproET-1 mRNA and ET-1-like-immunoreactivity (ET-1-ir) was seen over inflammatory cells and over airway epithelial cells. Some ET-1-ir was also located to bronchial and vascular smooth muscle cells. CONCLUSION: Increased cardiopulmonary ET synthesis strongly suggest a pathophysiological role for ET in CHF.

Endothelin receptor antagonist improves pulmonary hemodynamics during lung ischemia/reperfusion injury.

BACKGROUND: We have previously shown that elevated release of endothelin-1 is associated with increased pulmonary vascular resistance (PVR) immediately after reperfusion of the transplanted lung. In the present study, we investigated the effect of ET receptor blockage on pulmonary hemodynamics and function in an ex vivo lung reperfusion model after 6 hr of cold ischemia. METHODS: Eighteen rabbits were divided into three groups: no ischemia followed by 3 hr of reperfusion (group I) and 6 hr of cold ischemia followed by 3 hr of reperfusion with either blood (group II) or blood + SB209670 (mixed ETA/ETB receptor antagonist) (group III). RESULTS: Shortly after reperfusion, mean pulmonary artery pressure, PVR, and pulmonary edema were increased, and pulmonary compliance and PO2 were decreased in group II compared with group I. Treatment with SB209670 resulted in a significant decrease in mean pulmonary artery pressure, PVR, and pulmonary edema, and improvement in pulmonary compliance and PO2. CONCLUSION: The data suggest an important role for ET-1 in lung ischemia/reperfusion injury and that the use of ET receptor antagonist immediately after transplantation may provide a new therapeutic tool in the management of early graft dysfunction.

Nitric oxide and endothelin-1 in pulmonary hypertension.

BACKGROUND: We have shown previously increased expression of the potent vasoconstrictor peptide endothelin-1 (ET-1) in the pulmonary arteries of patients with pulmonary hypertension. We also demonstrated diminished expression of endothelial nitric oxide synthase, the enzyme responsible for generating nitric oxide (NO), in patients with the same disease. STUDY OBJECTIVE: To determine the expression of neuronal nitric oxide synthase (NOS-I) and endothelin-converting enzyme-1 (ECE-1) in lungs of patients with pulmonary hypertension. METHODS: Immunohistochemistry with avidin-biotin-peroxidase method. RESULTS: There was little immunostaining for NOS-I in the pulmonary arteries of normal control or diseased lungs. Moderate diffuse staining was seen in the airway epithelium and nerve bundles. Immunoreactivity for ECE-1 was seen in the airway epithelium, smooth muscle cells, and scattered macrophages of both normal and diseased lungs. Strong immunoreactivity for ECE-1 was seen in the endothelium of diseased pulmonary arteries of patients with pulmonary hypertension. CONCLUSION: We conclude that expression of NOS-I appears to be similar in normal and diseased lungs, while abundant expression of ECE-1 is present in diseased vessels, which may contribute to the pathogenesis of arteriopathy in pulmonary hypertension.

Production of endothelins by the ventilatory muscles in septic shock.

Circulating endothelin-1 (ET-1) concentration increases significantly in animal models of sepsis. The main mechanism responsible for this rise in ET-1 levels is believed to be upregulation of ET-1 synthesis in various organs, such as the lungs and heart. In this study we investigated whether ET-1 is synthesized in the ventilatory muscles and whether this synthesis is regulated in septic shock. Conscious rats were injected with Escherichia coli endotoxin (lipopolysaccharide [LPS]) and killed 6, 12, and 24 h later. A fourth group of rats was injected with normal saline and served as a control. The diaphragm was excised at the end of the experiment and quickly frozen. Diaphragmatic ET-1 level was measured with radioimmunoassay, and messenger RNA (mRNA) expression of ET-1 precursor prohormone (preproET-1), preproET-3, and endothelin-converting enzyme was measured with reverse transcription-polymerase chain reaction. LPS injection elicited an early (within 6 h) and prolonged rise in diaphragmatic ET-1 concentration. In addition, mRNA levels of preproET-1 and preproET-3 rose by about 4- and 3-fold within 6 to 12 h of LPS injection, whereas mRNA of endothelin-converting enzyme increased by more than 10-fold and peaked within 24 h of LPS injection. Immunostaining with anti-ET-1 antibody revealed positive ET-1 staining in the endothelium and somatic muscle fibers of septic diaphragms. These results indicate that diaphragmatic muscle fibers synthesize significant amounts of ET-1 in septic shock and that the rise in ET-1 production is due to upregulation of ET precursors and the converting enzyme.