Pulmonary metabolism of endothelin 1 during on-pump and beating heart coronary artery bypass operations

BACKGROUND: Coronary artery bypass operations are associated with increased circulating levels of the powerful vasoconstrictor endothelin 1. The pulmonary circulation is an important site for both production and clearance of endothelin 1. Lung endothelial injury resulting from cardiopulmonary bypass could modify pulmonary endothelin 1 metabolism through an increase in production, a reduction in removal, or a combination of both. METHODS: Pulmonary endothelin 1 kinetics were quantified by using the indicator-dilution technique in patients undergoing coronary artery bypass grafting with (n = 11) or without cardiopulmonary bypass (ie, beating heart; n = 10). Mixed venous endothelin 1 levels were also measured in samples from the pulmonary artery, and systemic levels were obtained from the radial artery. RESULTS: Pulmonary artery endothelin 1 levels were similar before and after cardiopulmonary bypass, with means of 1.59 +/- 0.37 pg/mL and 1.33 +/- 0.15 pg/mL (P =.45), respectively. Systemic endothelin 1 levels, however, increased after bypass from 1.64 +/- 0.22 pg/mL to 2.07 +/- 0.16 pg/mL (P =.01). In the beating heart group, endothelin 1 levels before and after the operation were similar in the pulmonary artery (1.25 +/- 0.27 pg/mL and 1.45 +/- 0.31 pg/mL, respectively; P =.38), as well as in the radial artery (1.70 +/- 0.26 pg/mL and 1.73 +/- 0.35 pg/mL, respectively; P =.92). The capacity to clear endothelin 1 from the pulmonary circulation, as computed from the permeability-surface area product for endothelin 1, was not affected by cardiopulmonary bypass before and after the operation (25.19 +/- 2.67 mL/s and 23.12 +/- 4.39 mL/s, respectively; P =.49). It was similar and also unaffected in the beating heart group. CONCLUSION: Coronary artery bypass grafting with cardiopulmonary bypass is associated with an increase in systemic endothelin 1 levels. The mechanism involved is not related to a decreased pulmonary clearance of endothelin 1 from the systemic circulation but rather to an increased endothelin 1 release by the lungs.     

Single lung transplantation in rats with chemically induced pulmonary hypertension.

Physiologic effects of single lung transplantation on pulmonary hypertension were studied in rats with monocrotaline-induced pulmonary hypertension. Inbred rats treated with monocrotaline (40 mg/kg) received a left lung isograft from a normal donor 2 weeks later, when pulmonary hypertension became significant (transplant group; n = 6). These rats and control rats treated with monocrotaline (mediated control group; n = 11) or vehicle alone (normal control group; n = 9) were followed up weekly by metabolic treadmill testing for exercise tolerance and oxygen consumption up to 6 weeks after monocrotaline (4 weeks after transplantation), when all rats underwent hemodynamic and histologic examinations. Whereas maximal oxygen consumption and exercise tolerance consistently deteriorated in the medicated control group of rats, indices in the transplant group stopped deteriorating 2 weeks after lung transplantation and remained at levels similar to those of normal control rats. Severe pulmonary hypertension (68 +/- 19 mm Hg) and right ventricular hypertrophy (right ventricular/left ventricular weight ratio, 0.95 +/- 0.19) were confirmed in medicated control rats in contrast to transplant animals, in which these two indices remained at normal control levels. Whereas left-to-right lung perfusion ratio was constant among rats not receiving transplants (0.69 +/- 0.16), it was significantly elevated (2.27 +/- 0.65; p less than 0.001) in those receiving transplants, suggesting preferential flow through the lung isograft. The results suggest that, in the early phase of pulmonary hypertension, single lung transplantation shifts pulmonary perfusion to the grafted lung, avoiding right ventricular pressure overload and thereby preserving exercise tolerance at a nearly normal level in rats with monocrotaline-induced pulmonary hypertension.     

Pulmonary vascular endothelial growth factor and nitric oxide interaction during total cardiopulmonary bypass in neonatal pigs

OBJECTIVE: Lung injury after cardiopulmonary bypass includes pulmonary hypertension and lung edema. Both complications are related to endothelial pulmonary vascular dysfunction, leukocyte sequestration, and increased capillary permeability. This study was done in an attempt to better define the endothelial dysfunction and the cause of edema. METHODS: Twenty-five neonatal piglets were subjected to total cardiopulmonary bypass for 90 minutes without crossclamping of the aorta. After weaning from cardiopulmonary bypass, they were allowed to survive 2 hours, at which time they were killed. Preoperative and postoperative hemodynamic studies, lung (n = 16) and muscular (n = 5) vascular endothelial growth factor contents, and exhaled nitric oxide (n = 8) were recorded. Immediately after the animals were killed, pulmonary arterial rings were obtained from 12 piglets and mounted in organ chamber for assessment of endothelial function with receptor-dependent (acetylcholine) or non-receptor-dependent (calcium ionophore A23187) studies and compared with control pulmonary arterial rings. The left lungs of 13 piglets were mounted in isolated perfused lung chambers for filtration coefficient assessment and comparison with control preparations. RESULTS: After cardiopulmonary bypass, pulmonary vascular resistance increased from 953.7 +/- 302.6 dyne x s x cm(-5) to 1973.6 +/- 925.4 dyne x s x cm(-5) (P =.03). This was associated with an increase in lung vascular endothelial growth factor content from 91.07 +/- 5.314 pg/100 mg tissue to 151.6 +/- 11.4 pg/100 mg tissue (P <.0001), an increase in muscle vascular endothelial growth factor from 76.02 +/- 11.53 pg/100 mg tissue to 81.58 +/- 7.7 pg/100 mg tissue (P not significant), and a decrease in exhaled nitric oxide from 6 +/- 1.7 ppb to 3.12 +/- 1.4 ppb (P =.003). The filtration coefficient was statistically significantly higher after cardiopulmonary bypass than in control preparations (0.259 +/- 0.02 vs 0.525 +/- 0.07, P <.0001). Variations in lung vascular endothelial growth factor accumulation were statistically significantly higher than in muscular vascular endothelial growth factor accumulation (60.5 +/- 9.1 vs 5.5 +/- 5.9, P =.0008). In addition, a statistically significant correlation was found between postbypass lung vascular endothelial growth factor and lung filtration coefficient (P =.0058), as well as between change in lung vascular endothelial growth factor and change in lung filtration coefficient (P =.03). Pulmonary vascular endothelial receptor-dependent (acetylcholine) function was statistically significantly blunted after bypass relative to control values (15.44% +/- 4.8% vs 55.5% +/- 5.96% of maximal relaxation, P =.0001), whereas non-receptor-dependent endothelial function was unaffected by cardiopulmonary bypass (110.77% +/- 8.9% vs 120.63% +/- 15.46% of maximal relaxation, P not significant). CONCLUSIONS: These findings suggest that lung ischemia that occurs during cardiopulmonary bypass affects the signal transduction from membrane receptors to intracellular calcium mobilization and nitric oxide synthase activation. Lung edema after bypass is probably due in part to lung accumulation of vascular endothelial growth factor, a finding that was not found in systemic muscular nonischemic territories.     

Gene transfer of hepatocyte growth factor with prostacyclin synthase in severe pulmonary hypertension of rats

Objective: Hepatocyte growth factor (HGF) is a multi-potent growth factor, which has anti-fibrotic effects for lung injuries. In this study, we investigated whether human HGF gene transfer may attenuate the medial hypertrophy of pulmonary arteries and enhance the ameliorating effect of prostacyclin in monocrotaline (MCT)-induced pulmonary hypertension in rats. Methods and results: The day before MCT injection, HVJ-liposome complex with the cDNA encoding HGF gene (H group), PGIS gene (P group), and both HGF and PGIS gene (HP group) were transfected to the liver of rats as drug delivery system for the lung. Rats transfected with control vector served as controls (C group). Twenty-eight days after MCT injection, histological examination showed marked thickening of medial wall of pulmonary arteries and right ventricular hypertrophy. Percent medial wall thickness (%WT) of peripheral pulmonary arteries, pressure ratio of the right ventricle (RV) to the left ventricle (LV), and weight ratio of the RV to the LV plus septum were significantly increased in the control. Percent medial wall thickness was significantly ameliorated in H group and HP group in comparison with C group. Pressure and weight ratio of RV to LV was significantly ameliorated in P group and HP group in comparison with C group, and was significantly ameliorated in HP group than P group. Conclusions: In vivo gene transfection with HGF gene attenuated the medial hypertrophy of pulmonary arteries and enhanced the ameliorating effect of prostacyclin for pulmonary hypertension in MCT rats. Thus, gene therapy with HGF and PGIS may be a promising strategy for severe pulmonary hypertension.     

Better preservation of endothelial function and decreased activation of the fetal renin-angiotensin pathway with the use of pulsatile flow during experimental fetal bypass

OBJECTIVE: Pulsatile flow was shown to overcome the progressive rise in peripheral and placental vascular resistances observed during steady-flow bypass, this rise being counteracted by inhibition of nitric oxide synthase. This study quantifies the release of endothelial vasoactive substances during a 60-minute in utero model of fetal bypass. METHODS: Fetuses were randomly allocated into 1 of 2 groups (steady flow, n = 8, or pulsatile flow, n = 13) and subjected to bypass through central cannulation and perfusion with either a centrifugal or pulsatile (125 beats x min(-1)) blood pump. RESULTS: Lactate concentration was high, starting at fetal exteriorization and increasing during fetal preparation in the 2 groups. Once bypass was established, the rise was significant only in the steady-flow group. Plasma nitric oxide metabolites, similar before bypass, reached higher levels during pulsatile flow at the end of bypass (99+/-9 vs. 82+/-23 micromol x L(-1); P =.037). Levels of urinary nitric oxide metabolites were significantly higher in the pulsatile-flow than in the steady-flow group (764+/-143 vs. 508+/-240 micromol x L(-1); P =.005). Plasma cyclic guanosine monophosphate levels increased after 30 minutes of bypass in the pulsatile-flow group (25+/-18 vs. 12+/-8 pmol x mL(-1); P =.004), and urinary cyclic guanosine monophosphate excretion was higher in the pulsatile-flow group (517+/-450 vs. 118+/-78 pmol x mL(-1); P =.024). Plasma endothelin-1 levels increased in the 2 groups and were higher in the steady-flow group at 30 minutes (27+/-5 vs. 23+/-2 pg x mL(-1); P =.04) and 60 minutes of bypass (39+/-7 vs 32 +/- 6 pg x mL(-1); P =.04). Plasma renin concentration increased significantly during bypass only in the steady-flow group (26+/-10 vs. 57+/-42 in ng A1 x mL(-1) x h(-1); P =.04). CONCLUSIONS: Improved placental and peripheral perfusion during fetal pulsatile-flow bypass may be mediated by preservation of fetal/maternal endothelial nitric oxide biosynthetic mechanisms and/or decreased activation of the fetal renin-angiotensin pathway.     

Cyclo-oxygenase products mediate hypoxic pulmonary hypertension

High-risk infants with a fetal pattern of circulation demonstrate hyperactivity of the pulmonary vascular bed in response to stimuli including mucous plugging, atelectasis, and endotrachial tube suctioning. The resultant increase in pulmonary vascular resistance (PVR) leads to pulmonary hypertension, severe right-to-left shunting, and hypoxemia. Stimuli that trigger pulmonary hypertension cause hypoxia, suggesting the importance of hypoxic pulmonary vasoconstriction (HPV). Although many humoral mediators of HPV have been hypothesized, none have been proven. This study investigates the possible role of the cyclo-oxygenase derivatives thromboxane A2 and prostacyclin as determinants of hypoxic pulmonary hypertension. Open-chested lambs were ventilated with 13% O2 prior to and following treatment with OKY 046, a selective thromboxane inhibitor. In untreated lambs, the partial pressure of arterial oxygen fell from 80 +/- 27 (mean +/- SD) to 35 +/- 13 mm HG (P less than .01). The mean arterial pressure (MAP) remained at 50 +/- 7 mm HG, and the cardiac output (CO) was unchanged at 0.8 +/- 0.2 L/min. The mean pulmonary arterial pressure (MPAP) rose from 11 +/- 4 to 20 +/- 4 mm HG (P less than .01) whereas the PVR increased 70% (P less than .01). TxB2 rose from 147 +/- 85 to 271 +/- 154 pg/mL (P less than .05), and 6-keto-PGF1 alpha rose from 105 +/- 96 to 142 +/- 110 pg/mL. These substances are the hydrolysis products of TxA2 and prostacyclin respectively. In animals treated with OKY 046 prior to ventilation with 13% O2, values for MAP, CO, and PVR were similar to those of the nontreatment period.(ABSTRACT TRUNCATED AT 250 WORDS)     

Hypertonic saline infusion for pulmonary injury due to ischemia-reperfusion

HYPOTHESIS: Inhibition of neutrophil-endothelial cell interactions by hypertonic saline (HTS) may confer protection against organ injury in states of immunologic disarray. This study tested the hypothesis that infusion of HTS modulates the development of end-organ injury in a model of lower-torso ischemia-reperfusion injury. DESIGN: Ischemia-reperfusion injury was induced in 30 male Sprague-Dawley rats by infrarenal aortic cross-clamp for 30 minutes, followed by reperfusion for 2 hours. At 0 and 60 minutes of reperfusion, intravenous HTS (7.5% sodium chloride, 4 mL/kg) was administered to 6 rats each, and another 12 received either 4 or 30 mL/kg of isotonic sodium chloride solution. Six rats received HTS, 4 mL/kg, before ischemia. At 2 hours, we assessed liver function, pulmonary injury, neutrophil infiltration (myeloperoxidase activity), endothelial permeability (bronchoalveolar lavage and wet-dry weight ratios), and proinflammatory cytokine levels (tumor necrosis factor alpha and interleukin 6). RESULTS: Infusion with HTS before or after ischemia significantly reduced end-organ injury. Histopathologic pulmonary injury scores were markedly attenuated in the HTS group (5.82 +/- 1.3) and the HTS pretreated group (4.91 +/- 1.6) compared with the isotonic sodium chloride solution groups (8.54 +/- 1.1) (P =.04). Pulmonary neutrophil sequestration (2.07 +/- 0.23) and increased endothelial permeability (4.68 +/- 0.44) were manifest in animals resuscitated with isotonic sodium chloride solution compared with HTS treatment (1.54 +/- 0.19 [P =.04] and 2.06 +/- 0.26 [P =.02]) and pretreatment (1.18 +/- 0.12 [P =.04] and 1.25 +/- 0.07 [P =.002]). In addition, a significant reduction in serum tumor necrosis factor alpha (P =.04) and interleukin 6 (P =.048) levels was observed, whereas HTS resuscitation attenuated the upsurge in aspartate transaminase (P =.03) and alanine transaminase levels (P =.047). CONCLUSIONS: Resuscitation with HTS attenuates the pulmonary edema and tissue injury due to lower-torso ischemia-reperfusion and maintains a more benign immunologic profile.     

Plasma brain natriuretic peptide as a noninvasive marker for efficacy of pulmonary thromboendarterectomy

BACKGROUND: Plasma brain natriuretic peptide (BNP), a cardiac hormone secreted mainly by the cardiac ventricles, has been shown to increase in proportion to the degree of cardiac overload. However, whether plasma BNP may serve as a marker for the efficacy of pulmonary thromboendarterectomy in patients with chronic thromboembolic pulmonary hypertension remains unknown. METHODS: Plasma BNP level was measured in 34 patients with chronic thromboembolic pulmonary hypertension before and 1 month after pulmonary thromboendarterectomy. Right heart catheterization was also performed before and 1 month after the operation. RESULTS: Preoperative plasma BNP level was significantly elevated in patients with chronic thromboembolic pulmonary hypertension compared with control patients (246 +/- 40 vs 13 +/- 2 pg/mL; p < 0.001; n = 34) and was positively correlated with total pulmonary resistance (r = 0.57; p < 0.001). After pulmonary thromboendarterectomy, plasma BNP level in survivors markedly decreased (220 +/- 31 to 54 +/- 9 pg/mL; p < 0.001; n = 32) in association with a reduction of total pulmonary resistance (15.6 +/- 1.0 to 4.5 +/- 0.3 Wood units; p < 0.001). The change in plasma BNP level was closely correlated with that in total pulmonary resistance (r = 0.63; p < 0.001). Importantly, a sustained elevation of plasma BNP (> or = 50 pg/mL) indicated the presence of residual pulmonary hypertension (> or = 5 Wood units) after operation (sensitivity = 73%; specificity = 81%). CONCLUSIONS: Plasma BNP level was strongly associated with the severity of pulmonary hypertension in patients with chronic thromboembolic pulmonary hypertension and thereby may serve as a noninvasive marker for the efficacy of pulmonary thromboendarterectomy.     

Serum levels of transforming growth factor beta1 in patients with breast cancer

HYPOTHESIS: Transforming growth factor beta1 (TGF-beta1) may be related to breast cancer progression. DESIGN: Prospective study. SETTING: University hospital. PATIENTS: Sixty consecutive patients with invasive breast cancer undergoing surgery were prospectively included and evaluated. The control group consisted of 14 patients with benign breast tumors (7 with fibrocystic disease and 7 with fibroadenoma). INTERVENTION: Venous blood samples were collected before the surgery. Sera were obtained by centrifugation and stored at -70 degrees C until assayed. Serum concentrations of TGF-beta1 were measured by quantitative sandwich enzyme immunoassay. Data on primary tumor stage, age, estrogen receptor status, lymph node status, distant metastases, and TNM staging (according to the Union Internationale Contre le Cancer) were reviewed and recorded. MAIN OUTCOME MEASURES: Measurements of preoperative serum TGF-beta1 levels in patients with breast cancer. RESULTS: The mean +/- SD value of serum TGF-beta1 in patients with invasive breast cancer was 498.7 +/- 249.7 pg/mL and in the control group was 495.2 +/- 225.5 pg/mL (P =.96). However, there were significantly higher serum levels of TGF-beta1 in patients with more advanced lymph node status (P =.04), more advanced TNM stage (P =.005), and poorer histological grade (P =.02). In multivariate analysis, TNM staging (P =.02) was demonstrated to be the independent factor related to significantly higher serum levels of TGF-beta1. CONCLUSIONS: Patients with more advanced TNM stages were shown to have higher serum TGF-beta1 levels. Thus, serum TGF-beta1 levels may reflect the severity of invasive breast cancer.     

Failure to show decrease in small pulmonary blood vessels in rats with experimental pulmonary hypertension.

We induced chronic pulmonary hypertension in one group of rats by exposing them to chronic hypobaric hypoxia (380 mm Hg for three weeks) and in another group by administering a single subcutaneous dose of monocrotaline (60 mg/kg body weight). Both groups of rats showed increase of the right ventricular mean systolic blood pressure and right ventricular hypertrophy. We measured the surface area of histological sections of the left or right lungs and counted all small blood vessels with an external diameter of less than 50 microns and with a definite elastic coat lying distal to respiratory bronchioles. In the 10 rats with chronic hypoxic pulmonary hypertension the mean total number of small pulmonary blood vessels was 428.8 +/- 96.9 (SD) compared with 337.8 +/- 91.9 in 10 untreated control rats. The number of small pulmonary blood vessels per mm2 of lung tissue was 4.0 +/- 1.3 in the chronically hypoxic rats compared with 3.8 +/- 1.2 in the controls. The mean total number of small pulmonary blood vessels in nine rats with monocrotaline-induced pulmonary hypertension was 396.8 +/- 61.7 compared with 384 +/- 55.4 in three control rats. The number of small pulmonary blood vessels per mm2 lung tissue was 3.3 +/- 0.6 in the rats treated with monocrotaline compared with 3.6 +/- 0.6 in the control group. We conclude that the number of small pulmonary blood vessels is not reduced in rats with pulmonary hypertension induced by chronic hypoxia or monocrotaline.     

The endothelin antagonist BQ123 reduces pulmonary vascular resistance after surgical intervention for congenital heart disease

OBJECTIVE: Postoperative pulmonary hypertension in children after surgical intervention for congenital heart disease has been attributed to failure of the pulmonary endothelium to provide adequate vasodilation. Although we have shown that the impaired vasodilatory component attributable to the l-arginine-nitric oxide pathway is almost completely reversible, a nonrestorable component persists, implying an additional vasoconstrictive mechanism in postoperative pulmonary endothelial dysfunction. In this study of children after surgical intervention for congenital heart disease, we measured endothelin-1 levels and used BQ123, a selective endothelin-A receptor antagonist, together with inhaled nitric oxide to discriminate dysfunctional pulmonary endothelial vasodilation from endothelin-mediated pulmonary vasoconstriction. METHODS: All children were examined early after surgical intervention in the intensive care unit. Pulmonary vascular resistance (with respiratory mass spectrometry), as well as arterial and venous endothelin-1 levels (measured by means of a quantitative enzyme-linked immunosorbent assay), were determined in 7 children (age range, 3.3-13.7 months; median age, 6.3 months) with intracardiac shunting defects at baseline and during ventilation with a fraction of inspired oxygen of 0.65, with additional BQ123 (0.1 mg/kg infused over 20 minutes), and with inhaled nitric oxide (20 ppm). RESULTS: Pulmonary vascular resistance decreased from 7.7 +/- 3.4 at baseline to 6.1 +/- 2.8 Woods units. m(-2) (P =.022) at a fraction of inspired oxygen of 0.65 and to 4.7 +/- 2.7 Woods units. m(-2) (P =.013) during BQ123 infusion. Inhaled nitric oxide had no further effect on pulmonary vascular resistance. Left atrial endothelin-1 levels (1.35-5.12 pg/mL; mean, 2.4 pg/mL) correlated significantly with the decrease in pulmonary vascular resistance in response to BQ123 infusion (r(2) = 0.89, P =.003). CONCLUSION: Postoperative elevation of pulmonary vascular resistance in children after surgical intervention for congenital heart disease is responsive to endothelin-A blockade with BQ123. Increased levels of endothelin-1 predict the response to this therapy, which might become an important addition to the clinical armamentarium in postoperative pulmonary hypertensive disease.     

血管活性物质在门肺高压症发病机制中的作用

目的 研究内皮素-1(ET-1)、一氧化氮(NO)、血栓素A2(TXA2)、前列环素(PGI2)、5 羟色胺(5-HT)和转移生长因子-β1(TGF-β1)在门肺高压症(PPHTN)发病机制中的作用.方法 对4 例PPHTN(P 组)和12 例PHT患者(C 组)进行病例-对照研究,另设10 例胃肠道肿瘤患者作为正常对...     

Secretion of A-type and B-type natriuretic peptides into the bloodstream and pericardial space in children with congenital heart disease

OBJECTIVE: To determine the secretion of A-type and B-type natriuretic peptides into the bloodstream and pericardial space in children with congenital heart disease. METHODS: Plasma and pericardial fluid samples were obtained from 77 patients undergoing total correction for congenital heart disease. All patients underwent detailed right-sided and left-sided cardiac catheterization preoperatively. RESULTS: A-type natriuretic peptide levels in pericardial fluid were lower than those in plasma (33.0 +/- 23.1 versus 39.8 +/- 33.6 pg/mL, P <.05), and B-type natriuretic peptide levels in pericardial fluid showed marked elevations compared with those in plasma (231.9 +/- 305.6 versus 19.8 +/- 29.3 pg/mL, P <.0001). The A-type and B-type natriuretic peptide levels in plasma correlated with those in pericardial fluid (R =.522, P <.0001; R =.595, P <.0001). For A-type and B-type natriuretic peptide levels in plasma, the relation with biventricular volume had the highest correlation (R =.669, P <.0001; R =.652, P <.0001). The patients with a pulmonary-to-systemic flow ratio greater than 2 (n = 19) had high levels of natriuretic peptides not only in plasma (58.3 +/- 43.2, 40.5 +/- 49.4 pg/mL, P <.05) but also in pericardial fluid (44.4 +/- 31.5, 287.2 +/- 198.5 pg/mL, P <.05), and higher correlation between A-type and B-type natriuretic peptide plasma levels and left ventricular volume (R =.913, P <.0001; R =.787, P <.0001). CONCLUSIONS: B-type natriuretic peptide is secreted not only into the bloodstream but also into the pericardial space in children with congenital heart disease. Natriuretic peptide levels in plasma correlated well with biventricular volume. The left ventricle was considered to be the main source of secreted natriuretic peptides in the patients with a pulmonary-to-systemic flow ratio greater than 2.     

Systemic lobar shunting induces advanced pulmonary vasculopathy

OBJECTIVES: We characterized the morphology and vasomotor responses of a localized, high-flow model of pulmonary hypertension. METHODS: An end-to-side anastomosis was created between the left lower lobe pulmonary artery and the aorta in 23 piglets. Control animals had a thoracotomy alone or did not have an operation. Eight weeks later, hemodynamic measurements were made. Then shunted and/or nonshunted lobes were removed for determination of vascular resistance and compliance by occlusion techniques under conditions of normoxia, hypoxia (FIO (2) = 0.03), and inspired nitric oxide administration. Quantitative histologic studies of vessel morphology were performed. RESULTS: Eighty-three percent of animals having a shunt survived to final study. Aortic pressure, main pulmonary artery and wedge pressures, cardiac output, blood gases, and weight gain were not different between control pigs and those receiving a shunt. Six of 9 shunted lobes demonstrated systemic levels of pulmonary hypertension in vivo. Arterial resistance was higher (24.3 +/- 12.0 vs 1.3 +/- 0. 2 mm Hg. mL(-1). s(-1), P =.04) and arterial compliance was lower (0. 05 +/- 0.01 vs 0.16 +/- 0.03 mL/mm Hg, P =.02) in shunted compared with nonshunted lobes. Hypoxic vasoconstriction was blunted in shunted lobes compared with nonshunted lobes (31% +/- 13% vs 452% +/- 107% change in arterial resistance, during hypoxia, P <.001). Vasodilation to inspired nitric oxide was evident only in shunted lobes (34% +/- 6% vs 1.8% +/- 8.2% change in arterial resistance during administration of inspired nitric oxide, P =.008). Neointimal and medial proliferation was found in shunted lobes with approximately a 10-fold increase in wall/luminal area ratio. CONCLUSIONS: An aorta-lobar pulmonary artery shunt produces striking vasculopathy. The development of severe pulmonary hypertension within a short time frame, low mortality, and localized nature of the vasculopathy make this model highly attractive for investigation of mechanisms that underlie pulmonary hypertension.     

Effects of cardiopulmonary bypass on eicosanoid metabolism during pediatric cardiovascular surgery

Cardiopulmonary bypass in children with congenital heart disease is associated with significant morbidity manifested by increased complement degradation products, heightened pulmonary vascular activity, and coagulopathy. In adults with cardiac disease, the prostaglandins (eicosanoids) have been shown to contribute to the pathophysiologic response to extracorporeal circulation. This study assessed the effect of cardiopulmonary bypass in infants and children on two potent eicosanoids: thromboxane, a vasoconstrictor and platelet aggregating agent, and prostacyclin, a vasodilator and platelet disaggregating agent. The biochemical profiles of thromboxane and prostacyclin were evaluated in temporal relationship to selected parameters of platelet loss and pulmonary vascular hemodynamics during and after cardiopulmonary bypass. Twenty-one children, aged 3 days to 9 years, with congenital heart defects who were undergoing repair with cardiopulmonary bypass were studied. Nine pediatric patients undergoing palliative heart operations with no cardiopulmonary bypass served as the control group. In the group having cardiopulmonary bypass, the thromboxane concentration significantly increased during bypass (195 +/- 10 to 910 +/- 240 pg/ml, +/- standard error of the mean, p less than 0.005), whereas the control group demonstrated no significant change in thromboxane concentration. The highest thromboxane values were seen in the youngest patients (p less than 0.002). There was no significant correlation between thromboxane changes with alterations in pulmonary vascular resistance, platelet loss, duration of cardiopulmonary bypass or aortic cross-clamping. Prostacyclin levels rose significantly in both the bypass group (100 +/- 20 to 570 +/- 80 pg/ml, p less than 0.01) and in the control group (109 +/- 44 to 589 +/- 222 pg/ml, p less than 0.01), which apparently is due to surgical manipulation of vascular endothelium. These data show that eicosanoid production is significantly altered in children during cardiopulmonary bypass. Although thromboxane, a potent vasoconstrictor, is produced in significant amounts during and after cardiopulmonary bypass, our data show that thromboxane does not directly mediate changes in pulmonary artery hypertension and is not quantitatively related to platelet loss during pediatric cardiovascular operations.     

In vivo adenovirus-mediated endothelial nitric oxide synthase gene transfer ameliorates lung allograft ischemia-reperfusion injury

OBJECTIVE: Nitric oxide regulates vascular tone, inhibits platelet aggregation, and inhibits leukocyte adhesion, all of which are important modulators of ischemia-reperfusion injury. This study aimed to determine the effects of endothelial constitutive nitric oxide synthase gene transfer on ischemia-reperfusion injury in a rat lung transplant model. METHODS: In group I, donor animals were injected intravenously with 5 x 10(9) pfu of adenovirus-encoding endothelial constitutive nitric oxide synthase. Groups II and III served as controls, whereby donor animals were injected with either 5 x 10(9) pfu of adenovirus encoding beta-galactosidase or saline solution, respectively. Twenty-four hours after injection, left lungs were harvested and preserved for 18 hours at 4 degrees C, then implanted into isogeneic recipients, which were put to death 24 hours later. Recombinant endothelial constitutive nitric oxide synthase gene expression was evaluated by Western blotting and immunohistochemistry. Lung grafts were assessed by measuring arterial oxygenation, myeloperoxidase activity, and wet/dry weight ratios. RESULTS: Western blotting confirmed the overexpression of endothelial constitutive nitric oxide synthase in lungs so transfected compared with controls. Twenty-four hours after reperfusion, mean arterial oxygenation was significantly improved in group I compared with group II and III controls (189.4 +/- 47.1 mm Hg vs 71.7 +/- 8.9 mm Hg and 67.8 +/- 12.2 mm Hg, P =.02, P =.01, respectively). Myeloperoxidase activity, a reflection of tissue neutrophil sequestration, was also significantly reduced in group I compared with groups II and III (0.136 +/- 0.038 DeltaOD/mg/min vs 0. 587 +/- 0.077 and 0.489 +/- 0.126 DeltaOD/mg/min, P =.001, P =.01, respectively). CONCLUSION: Adenovirus-mediated gene transfer with endothelial constitutive nitric oxide synthase ameliorates ischemia-reperfusion injury as manifested by significantly improved oxygenation and decreased neutrophil sequestration in transplanted lung isografts. Endothelial constitutive nitric oxide synthase gene transfer may reduce acute lung dysfunction after lung transplantation.     

Recombinant bactericidal/permeability-increasing protein attenuates the systemic inflammatory response syndrome in lower limb ischemia-reperfusion injury

OBJECTIVES: Hind limb ischemia-reperfusion (I/R) injury increases gut permeability, and resultant endotoxemia is associated with an amplified systemic inflammatory response syndrome leading to multiple organ dysfunction syndrome. We studied the potential role of recombinant bactericidal/permeability-increasing protein (rBPI(21) ), a novel antiendotoxin therapy, in modulating endotoxin-enhanced systemic inflammatory response syndrome in hind limb I/R injury. METHODS: In this prospective, randomized, controlled, experimental animal study, 48 male Wistar rats, weighing 300 to 350 g, were randomized to a control group (sham) and five groups undergoing 3 hours bilateral hind limb ischemia with 2 hours reperfusion (I/R) (n = 8 per group). The control and untreated I/R groups received thaumatin, a control-protein preparation, at 2 mg/kg. Treatment groups were administered rBPI(21) intravenously at 1, 2, or 4 mg/kg body weight at the beginning of reperfusion; an additional group was administered rBPI(21) intravenously at 2 mg/kg after 1 hour of reperfusion. Plasma interleukin-6 concentration was estimated by bioassay as a measure of systemic inflammation. Plasma endotoxin concentration was determined by use of an amebocyte lysate chromogenic assay. Crossreactive immunoglobulin G and M antibodies to the highly conserved inner core region of endotoxin were measured by use of an enzyme-linked immunosorbent assay. The lung tissue wet-to-dry weight ratio and myeloperoxidase concentration were used as markers of edema and neutrophil sequestration, respectively. RESULTS: I/R provoked highly significant elevation in plasma interleukin-6 concentrations (1351.20 pg/mL [860.16 - 1886.40 pg/mL]) compared with controls (125.32 pg/mL [87.76-157.52 pg/mL; P <.0001]), but treatment with rBPI(21) 2 mg/kg at onset of reperfusion (715.89 pg/mL [573.36-847.76 pg/mL]) significantly decreased interleukin-6 response compared with the nontreatment group ( P <.016). I/R increased plasma endotoxin concentrations significantly (21.52 pg/mL [6.20-48.23 pg/mL]), compared with control animals (0.90 pg/mL [0.00-2.30 pg/mL; P <.0001]), and treatment with rBPI(21) 4 mg/kg at reperfusion significantly decreased endotoxemia (1.30 pg/mL [1.20-2.20 pg/mL]), compared with the untreated group ( P <.001). The lung tissue myeloperoxidase level was significantly increased in the untreated I/R group (208.18% [128.79%-221.81%]), compared with in controls (62.00% [40.45%-80.92%; P <.0001]), and attenuated in those treated with rBPI(21) 2 mg/kg (129.54% [90.49%-145.78%; P <.05]). Data represent median and interquartile range, comparisons made with the nonparametric Mann-Whitney U test. CONCLUSIONS: These findings show that hind limb ischemia-reperfusion injury is associated with endotoxemia, elevations in plasma interleukin-6, and pulmonary leukosequestration. Treatment with rBPI(21) after ischemia reduces endotoxemia, the interleukin-6 response, and attenuates pulmonary leukosequestration in response to hind limb reperfusion injury.