Fetal erythropoietin and endothelin-1: relation to hypoxia and intrauterine growth retardation.

BACKGROUND: We have examined whether endothelin-1 (ET-1) and erythropoietin (EPO) in amniotic fluid, and EPO in fetal serum obtained by cordocentesis from fetuses with signs of intrauterine growth retardation (IUGR), were correlated to fetal growth and/or chronic fetal hypoxia. METHODS: Amniotic fluid and fetal serum were obtained by cordocentesis from 28 fetuses suspected to have IUGR and subsequently analyzed for EPO and ET-1 by ELISA. These data were correlated to blood gas results and fetal/maternal parameters at delivery. RESULTS: A novel finding was that ET-1 correlated to PO2 in amniotic fluid. The average level of ET-1 in amniotic fluid was 48.3+/-4.7 pmol/L. The results also showed a correlation between EPO levels in amniotic fluid and EPO in fetal serum. Furthermore, EPO correlated weakly to birth weight at delivery. Children with the lowest birth weights had the highest EPO levels. High EPO values, similarly to ET-1, correlated to low pO2 values. The level of EPO in amniotic fluid was 8.0+/-1.6 mIU/ml and in cord blood 29.5+/-9.6 mIU/ml. CONCLUSIONS: The results indicate that ET-1 levels may be a marker for short-term hypoxia, but not for fetal growth, since ET-1 in amniotic fluid was correlated to PO2 at the time of cordocentesis, but not to birth weight. The results also indicate that EPO levels in amniotic fluid and in fetal cord serum are highly correlated, and thus both can be used as markers for fetal growth and chronic hypoxia before the onset of labor.

Hemodynamic effects of endothelin-1 and big endothelin-1 in chronic hemodialysis patients.

Increased plasma concentrations of endothelin-1 (ET-1) and big endothelin-1 (big ET-1) have been reported in patients with end-stage renal failure (ESRD). In the present study, which included hemodialysis (HD) patients with (n = 21) and without (n = 32) ischemic heart disease, the putative association between plasma levels of ET-1 and big ET-1 and ischemic heart disease and the influence of the dialysis procedure on ET concentrations was investigated. This study also examined in an additional five HD patients without cardiac disease whether intravenously infused ET-1 and big ET-1 (0.2, 1, and 4 pmol/kg per min, each dose for 20 min) preserve their vasoactive potency and whether exogenous big ET-1, which in healthy humans is converted in the kidney, is still converted to ET-1 in ESRD. HD patients with ischemic heart disease demonstrated higher plasma levels of ET-1 and big ET-1 than HD patients without this disorder, and HD reduced plasma ET-1 and big ET-1 concentrations. In HD patients, the big ET-1 infusion, resulting in a 1.5-fold increase in plasma ET-1, caused a more marked and prolonged rise in mean arterial BP than ET-1 (20% versus 13%, P = 0.0001) and a slightly smaller but more prolonged decrease in estimated splanchnic blood flow than ET-1 (37% versus 44%, P = 0.02). Furthermore, big ET-1 lowered heart rate by 9% (P = 0.01) but ET-1 did not. Plasma half-lives of ET-1 and big ET-1 were longer in HD patients than in healthy humans. Thus, ET-1 and big ET-1 preserve their vasoactive potency, and circulating big ET-1 is still converted to active ET-1 in ESRD. Consequently, the increased plasma levels of ET-1 and big ET-1 noted in HD patients, especially in patients with ischemic heart disease, might play a role in the development of uremic cardiovascular complications.

The C-terminal fragment of big endothelin-1 does not potentiate the vasoactive effects of endothelin-1.

The aim was to study the cardiovascular effects of the C-terminal (22-38) fragment of big endothelin-1, which is produced by the cleavage of big endothelin-1 (big ET-1) to endothelin-1 (ET-1). An intravenous infusion of the (22-38) fragment (4, 8 and 12 pmol kg-1 min-1, each dose for 10 min) was given to 10 healthy subjects. Four control subjects received 0.9% saline. Two additional subjects received ET-1 1 (0.2 and 4 pmol kg-1 min-1, each dose for 20 min) alone or combined with an equimolar infusion of the (22-38) fragment on two separate occasions. The fragment infusion did not alter heart rate, mean arterial blood pressure, cardiac output, systemic or pulmonary vascular resistance, splanchnic, cerebral or forearm blood flow. Renal blood flow showed a slight fall (11%, P < 0.001) in the fragment group of the same magnitude as in a previous control study. After the fragment infusion, a decrease in mean pulmonary arterial pressure (MPAP) by 12% (P < 0.01) and in pulmonary capillary wedge pressure (PCWP) by 31% (P < 0.001) was noted, which did not differ from the pulmonary pressures in the saline-infused control group. The (22-38) fragment, when combined with ET-1, was not able to modify the effects of ET-1 on heart rate, mean arterial blood pressure, splanchnic and renal blood flow. Consequently, the exogenous (22-38) fragment does not seem to cause any significant cardiovascular effects in healthy humans.

The endothelin receptor antagonist, bosentan, in combination with the cyclooxygenase inhibitor, diclofenac, counteracts pulmonary hypertension in porcine endotoxin shock.

OBJECTIVE: To prevent endotoxin-induced pulmonary hypertension in the pig with a combination of a nonpeptide mixed endothelin receptor antagonist, bosentan, and a cyclooxygenase inhibitor, diclofenac. DESIGN: Prospective, controlled trial. SETTING: Animal laboratory at a large university medical center. SUBJECTS: Twelve domestic pigs, weighing 17.5 to 27 kg. INTERVENTIONS: Endotoxin shock was induced by intravenous infusion of Escherichia coli lipopolysaccharide endotoxin (15 micrograms/kg/hr). Six pigs receiving only endotoxin served as controls. Six pigs were pretreated with intravenous bolus injections of bosentan (5 mg/kg) and diclofenac (3 mg/kg) followed by a continuous bosentan infusion (2.5 mg/kg/hr). MEASUREMENTS AND MAIN RESULTS: Systemic hemodynamics and regional circulation were measured using ultrasonic flow probes. Arterial and mixed venous blood samples were collected regularty for determination of Big endothelin-1-like immunoreactivity, endothelin-1-like immunoreactivity, norepinephrine, and blood gases. The bosentan/diclofenac pretreatment per se significantly decreased mean pulmonary arterial pressure (p < .001), pulmonary vascular resistance index (p < .001), and mean arterial blood pressure (p < .001), but cardiac index did not change. Splenic blood flow increased (p < .01) while renal blood flow decreased (p < .001). In addition, intestinal blood flow decreased slightly (p < .05). In the control group, only three animals survived the 3 hrs of endotoxin infusion, while all pretreated animals survived. The biphasic increase in mean pulmonary arterial pressure and pulmonary vascular resistance index seen in control animals during endotoxemia was markedly attenuated in animals pretreated with the bosentan/diclofenac combination. The pretreated group generally showed a favorable hemodynamic course, with a relatively higher cardiac index, stroke volume index, and splenic and renal blood flow. In control animals, a pronounced metabolic acidosis developed during endotoxin infusion. A relatively higher arterial plasma concentration of endothelin-1-like immunoreactivity was reached in pretreated animals, while the Big endothelin-1-like immunoreactivity plasma increase was similar in both groups. Arterial concentrations of norepinephrine were significantly (p < .01) higher in control animals when compared with diclofenac/bosentan-treated animals. CONCLUSIONS: The combination of bosentan and diclofenac induced systemic and pulmonary vasodilation in the intrinsic state. During endotoxin shock, this drug combination efficiently counteracts pulmonary hypertension and improves cardiac performance and splenic and renal blood flow. These favorable circulatory effects may have resulted in a reduction of both sympathetic nervous system activation and metabolic acidosis. Thus, we conclude that the endothelin receptors participate in intrinsic regulation of vascular tone in the anesthetized pig. During endotoxin shock, blockade of these receptors, as well as inhibition of the cyclooxygenase enzymes, contributes to a less adverse effect on the systemic and pulmonary circulation.

Plasma endothelin in normal and diabetic pregnancy.

OBJECTIVE: To examine endothelin-1 (ET-1) concentrations longitudinally throughout pregnancy in healthy and insulin-dependent diabetic women and to evaluate the relationship between ET-1 and big ET-1 in normal pregnancy. RESEARCH DESIGN AND METHODS: Venous blood samples were obtained consecutively in gestational weeks 18, 28, and 38 from 40 healthy women with uneventful pregnancies and 24 pregnant women with IDDM. By radioimmunoassay, plasma ET-1 and big ET-1 were analyzed in the healthy women and plasma ET-1 in the diabetic women. RESULTS: In the diabetic pregnant women, plasma ET-1 levels were significantly higher than in healthy pregnant women during the entire observation period (P < 0.001), but did not change with advancing gestational age. Five of the diabetic, but none of the healthy pregnant women, developed preeclampsia. ET-1 levels did not differ between the diabetic women who developed preeclampsia and those who did not. Plasma ET-1 levels in healthy pregnant women were within the range of those in healthy nonpregnant women and did not change during pregnancy. The big ET-1 levels increased and the ET-1/big ET-1 ratio decreased significantly during the observation period. CONCLUSIONS: Plasma ET-1 levels do not change with advancing gestational length. During normal pregnancy, the ET-1/big ET-1 ratio decrease, indicating a suppressed converting enzyme activity or altered clearance of ET-1. Pregnant women with IDDM have markedly elevated ET-1 levels. Although diabetic women with and without preeclampsia did not differ with respect to endothelial dysfunction, as reflected by elevated ET-1 concentration, we cannot exclude that altered endothelial function may be of importance for the increased frequency of preeclampsia in pregnant IDDM patients.

Endothelin-1 and big endothelin-1 levels in normal term pregnancy and in preeclampsia.

To study the concentrations of endothelin-1 (ET-1) and its precursor, big ET-1, in samples of amniotic fluid, fetal urine, umbilical arterial and venous blood, retroplacental blood and maternal uterine and brachial venous blood obtained from normal and preeclamptic women. Samples were collected from 31 healthy pregnant women (16 in labor and 15 undergoing elective cesarean section) and 35 preeclamptic women (9 in labor and 26 undergoing cesarean section). Big ET-1 and ET-1 were measured by radioimmunoassay and the ET-1 to big ET-1 ratios were calculated. In preeclamptic women there was a significant elevation of ET-1 in the maternal brachial and uterine veins and of big-ET-1 in the brachial vein. The ET-1 concentrations and the ET-1/big ET ratios were significantly higher on the fetal side (i.e., in the umbilical vein and amniotic fluid) than in maternal blood, but in these sampling locations there was no difference between the normal pregnancy and preeclampsia group. A significant negative correlation (r = -0.67, P < 0.01) was found between plasma ET-1 in the umbilical vein and birth weight in the preeclamptic group. ET-1 was significantly higher in amniotic fluid than in the first neonatal urine of corresponding pregnancies (15.0 +/- 2.0 vs. 3.0 +/- 2.9 pmol/l, P < 0.05). The ET-1 and big ET-1 concentrations are significantly higher in fetal plasma and amniotic fluid than in maternal plasma, indicating increased endothelin converting enzyme activity and increased ET-1 production in utero. The elevated ET-1 concentration in maternal blood in preeclamptic compared with normal pregnant women and the negative correlation between ET-1 in the umbilical vein and birth weight suggest that ET-1 plays a pathophysiological role in preeclampsia and other conditions with intrauterine growth restriction.

Effects of Ro 47-0203 and PD155080 on the plasma kinetics, receptor binding and vascular effects of endothelin in the pig.

The effects of the mixed endothelin ET(A)/endothelin ET(B) receptor antagonist Ro 47-0203 (bosentan, 4-tert-butyl-N-[6-(2-hydroxy-ethoxy)-5-( 2-methoxy -phenoxy)-2,2'-bipyrimidin-4-yl] -benzenesulfonamide) and the selective endothelin ET(A) receptor antagonist PD155080 (sodium 2-benzo[1,3]dioxol-5-yl-3-benzyl-4-(4-me thoxy-phenyl)-4-oxobut+ ++-2-enoate) on plasma half-life and regional extraction of exogenous endothelin-1 as well as on the regional vascular effects of endothelin-1 were investigated in the pig in vivo. Bosentan but not PD155080 (5 mg/kg, i.v. bolus, both drugs) increased the arterial plasma levels of endothelin-1-like immunoreactivity. Neither of the drugs affected the plasma half-life of infused endothelin-1. In the spleen, both the extraction and vascular effects of exogenous endothelin-1 were attenuated by both bosentan and PD155080 whereas renal extraction and vascular effects in the kidney were unaffected by both drugs. In the lung, only bosentan decreased pulmonary extraction of endothelin-1. In conclusion, the bosentan-induced increase of circulating endothelin-1 seems to be related to blockade of endothelin-1 binding to endothelin ET(B) receptors. Blockade of these receptors does not influence the overall elimination of endothelin-1, however.

The effect of endothelin receptor blockade on the development of the Sephadex-induced inflammation in the rat lung.

The non-peptide ET-receptor antagonist Bosentan was used to investigate the role of endogenous endothelin-1 (ET-1) in the development of the Sephadex-induced lung inflammation in the rat. Intratracheal instillation of Sephadex caused a 60-fold rise in endothelin-1-like-immunoreactivity (ET-1-LI) in bronchoalveolar lavage fluid (BALF) concomitant with development of lung oedema, an influx of inflammatory cells into the airways and a rise in the protein content in BALF. The ET-1-LI level in lung homogenate was not significantly affected. Pre-treatment with Bosentan reduced ET-1-LI content in the lung parenchyma but increased ET-1-LI levels in BALF, possibly indicating an effective displacement of ET-1 from its receptors. In Bosentan-treated animals there was an enhancement of the lung oedema formation following Sephadex instillation, but no significant change in the number of leucocytes or protein concentration in BALF. The present data thus do not support the hypothesis that endogenous ET-1 mediates oedema formation or leucocyte influx in this model. If anything, Bosentan enhanced the oedema formation in parallel with increased ET-1-LI in BALF.

Increased concentrations of endothelin-1 messenger RNA in tissues and endothelin-1 peptide in plasma in septic pigs: modulation by betamethasone.

OBJECTIVES: To study the expression of preproendothelin-1 messenger RNA (mRNA) in tissue after Escherichia coli lipopolysaccharide challenge and to evaluate the possible effects of betamethasone both regarding endothelin-1 production as well as hemodynamic and vascular effects during E. coli lipopolysaccharide infusion in pigs in vivo. DESIGN: Prospective trial. SETTING: Laboratory at a university medical center. SUBJECTS: Ten domestic pigs, weighing 18 to 25 kg. INTERVENTIONS: Anesthetized pigs were given continuous infusions of E. coli lipopolysaccharide (15 micrograms/kg/hr for 3 hrs), with or without prior treatment with betamethasone (0.5 mg/kg im 12 hrs before the start of the surgical preparation and 0.5/kg iv at the start of the preparation). MEASUREMENTS AND MAIN RESULTS: The E. coli lipopolysaccharide infusion evoked the characteristic cardiovascular changes observed in septic shock: decreased mean arterial pressure and cardiac output; increased heart rate and increased pulmonary vascular resistance. Large increases in both arterial plasma concentrations of endothelin-1-like immunoreactivity, as well as preproendothelin-1 mRNA concentrations in tissues, were also observed during the E. coli lipopolysaccharide infusion. Treatment with betamethasone significantly attenuated the E. coli lipopolysaccharide-induced increase in endothelin-1 plasma concentrations, whereas the increased mRNA concentrations were only slightly affected. Furthermore, betamethasone treatment also affected cardiovascular parameters, with significant attenuation of the E. coli lipopolysaccharide-induced increase in heart rate and a higher cardiac output after 60 mins of the E. coli lipopolysaccharide infusion. The urine production, which was markedly decreased during the E. coli lipopolysaccharide infusion, was significantly higher in the betamethasone-treated group compared with the control group. CONCLUSIONS: The present results indicate that the increased concentrations of endothelin-1-like immunoreactivity that are observed in septic shock may have negative effects on both cardiovascular parameters as well as renal function, which is in agreement with a possible role for endothelin-1 in the pathogenesis of septic shock.

Central and regional hemodynamic effects during infusion of Big endothelin-1 in healthy humans.

Big endothelin-1 (Big ET-1) was given intravenously to six healthy men to study uptakes and vascular effects. Blood samples were taken from systemic and pulmonary arterial and internal jugular and deep forearm venous catheters. Arterial Big ET-1-like immunoreactivity (Big ET-1-LI) increased from 5.43 +/- 0.60 to 756 +/- 27 pmol/l, and ET-1-LI increased from 4.67 +/- 0.08 to 6.67 +/- 0.52 pmol/l (P < 0.001). Skeletal muscle fractional extraction of Big ET-1-LI was 15 +/- 4%. ET-1-LI release did not increase in the studied vascular beds. Heart rate fell by 17% (P < 0.001), cardiac output fell by 26% (P < 0.001), and stroke volume fell by 11% (P < 0.05). Mean arterial blood pressure increased 18%, systemic vascular resistance increased 65%, and pulmonary vascular resistance increased 57% (P < 0.01-0.001). Pulmonary blood pressures, forearm blood flow, arterial pH, arterial PCO2, and systemic arterial-internal jugular venous O2 difference remained unchanged. No specific Big ET-1 receptors were found in human pulmonary membranes. The half-maximal inhibitory concentration for the receptor antagonist bosentan was 181 nM. In summary, circulating Big ET-1 elicits greater increases in mean arterial blood pressure and systemic vascular resistance and decreases in heart rate and cardiac output compared with an equimolar ET-1 infusion (26).

Bosentan-improved cardiopulmonary vascular performance and increased plasma levels of endothelin-1 in porcine endotoxin shock.

1. To evaluate the possible contribution of endothelin-1 (ET-1) to the pathophysiology of porcine septic shock, the non-peptide, mixed ET-receptor antagonist, bosentan (RO 47-0203) was administered (5 mg kg-1, i.v.) 30 min before infusion of lipopolysaccharide (LPS) (E. coli., serotype 0111:B4) (15 micrograms kg-1 h-1) and at 3.5 h of endotoxaemia in six anaesthetized and mechanically ventilated pigs. Six other pigs served as controls and received only LPS infusion. Pulmonary and systemic haemodynamics as well as splenic, renal and intestinal blood flows were measured continuously. Release and synthesis of ET-1 and Big ET-1 were also measured. 2. Only three of the six pigs in the control group survived 3 h of LPS infusion while in the bosentantreated group all six pigs were alive at that time. A biphasic increase in mean pulmonary arterial pressure (MPAP) and pulmonary vascular resistance (PVR) was seen in control pigs. Pretreatment with bosentan did not influence the first peak but markedly attenuated the second, more prolonged increase in MPAP and PVR. The second dose of bosentan completely restored these parameters to pre-LPS levels. The LPS-induced changes in mean arterial blood pressure, heart rate and systemic vascular resistance were similar in both groups, while cardiac output (CO) was significantly higher in the bosentan-treated group. The second bosentan dose increased CO and splenic and intestinal blood flow without further lowering of blood pressure. 3. Bosentan caused an increase of the basal arterial plasma levels of ET-1-like immunoreactivity (LI), from 16.8 +/- 1.3 pM to 49.6 +/- 10.0 pM (n = 6, P < 0.01). However, the rate of the increase of ET-1 levels during the LPS infusion was not affected by bosentan. Repeated administration of bosentan during LPS infusion caused an additional increase of ET-1-LI levels. Neither the basal levels of Big ET-LI nor the LPS induced 8 fold increase in Big ET-LI were changed by bosentan. The level of preproET-1 mRNA in the lung was increased about 3 fold after 4.5 h of LPS treatment. This elevation was not influenced by bosentan. 4. From these studies using bosentan, a non-peptide, selective and mixed ET-receptor antagonist, we conclude that during LPS-induced shock bosentan can abolish the late phase pulmonary hypertension and improve cardiac output as well as increase blood flow to the splenic and intestinal vascular beds without causing a further decrease in mean arterial blood pressure. Further investigations in the clinical setting are needed to evaluate the use of ET-receptor antagonists, such as bosentan, in treatment of septic shock.

Release of endothelin-1 into rat airways following Sephadex-induced inflammation; modulation by enzyme inhibitors and budesonide.

The intratracheal (i.t.) instillation of Sephadex beads into rat induced inflammation and a 30-fold increase in the endothelin-1-like immunoreactivity (ET-1-LI) of broncho-alveolar lavage fluid. The levels were highest 24 h after the instillation and had declined significantly after 48 h. At a dose of 1 mg kg-1 i.t., the glucocorticosteroid budesonide almost abolished this response. Phosphoramidon, which inhibits neutral endopeptidase, an enzyme reported to degrade ET-1 and also to inhibit the endothelin-converting enzyme, potentiated the Sephadex-induced rise in ET-1-LI. Chymostatin and heparin, which are reported to reduce the formation of ET-1, did not affect the increase in ET-1-LI. The present model represents a very reactive system for analyzing the changes in ET-1 levels during inflammation.

Myocardial release of endothelin (ET) and enhanced ET(A) receptor-mediated coronary vasoconstriction after coronary thrombosis and thrombolysis in pigs.

We investigated changes in vascular reactivity to endothelin (ET) and local release of ET-like immunoreactivity (ET-LI) induced by myocardial ischemia and reperfusion in a pig model of coronary thrombosis and thrombolysis and studied the possible mechanisms producing the changed vascular reactivity to ET-1. We induced coronary thrombosis by inserting a copper coil into the left anterior descending coronary artery (LAD) and achieved thrombolysis with tissue plasminogen activator (t-PA). Vascular reactivity to ET-1 in the nonischemic and ischemic/reperfused LAD diagonal branches was evaluated in vitro. ET-LI was analyzed in plasma from the great cardiac vein and aorta for estimation of local release. The vasoconstrictor response to ET-1 was enhanced twofold (p < 0.01) in the ischemic/reperfused arteries as compared with the nonischemic arteries. The vasoconstriction induced by the ETB receptor agonist [Ala 1,3,11,15] ET-1 or serotonin was not significantly affected by ischemia/reperfusion. The ETA receptor antagonist BQ-123 reversed the ET-1-induced vascular contraction to a similar degree in ischemic/reperfused and control arteries. The ET-1-induced vasoconstriction of control arteries was not affected by inhibition of nitric oxide (NO) synthase with NG-nitro-L-arginine (L-NNA) or cyclooxygenase with indomethacin. During reperfusion, the myocardial venoarterial plasma concentration difference of ET-LI and blood flow increased, resulting in an increased overflow of ET-LI. Our results demonstrate that coronary thrombosis and thrombolysis evokes enhanced local release of ET-LI during the reperfusion period and increases the vasoconstrictor effects of ET-1 through a mechanism related to ETA receptor activation but unrelated to altered endothelial function. These changes may play a role in the development of ischemic/reperfusion injury and no-reflow phenomenon.

ET-3 is extracted by and induces potent vasoconstriction in human splanchnic and renal vasculatures.

To investigate splanchnic and renal vascular effects and elimination of endothelin-3 (ET-3), ET-3 (10 pmol.kg-1.min-1 iv for 20 min) was given to six healthy male volunteers. Arterial plasma ET-3-like immunoreactivity (ET-3-Li) increased 10-fold to 111 +/- 31 pmol/l (P < 0.01). The initial half-life of plasma ET-3-Li determined in three subjects was 1.7 +/- 0.2 min. The fractional extraction of ET-3-Li was 68 +/- 7% in the splanchnic and 63 +/- 4% in the renal vascular beds. Mean arterial blood pressure fell from 86 +/- 4 to 94 +/- 4 mmHg (10%) (P < 0.05). Splanchnic and renal blood flows fell by 43 +/- 3% (P < 0.05) and 29 +/- 4% (P < 0.05), respectively, during the infusion. Splanchnic and renal vascular resistances rose by 92 +/- 22% (P < 0.05) and 58 +/- 7% (P < 0.05). In conclusion, ET-3 infusion in humans induces splanchnic and renal vasoconstriction of similar magnitude as previously shown during endothelin-1 infusion, presumably by ETB receptor activation. Plasma ET-3 is efficiently extracted in the splanchnic and renal vascular regions.

Effect of allergen provocation on inflammatory cell profile and endothelin-like immunoreactivity in guinea-pig airways.

The effect of allergen challenge on the number of leucocytes and the concentration of endothelin 1-like immunoreactivity (ET-LI) in bronchoalveolar lavage fluid (BALF) was investigated in guinea-pigs sensitized to Ascaris suum. The animals were twice exposed to allergen aerosol. All animals responded to the second challenge with bronchoconstriction. Twelve hours later, a significant increase in the number of eosinophilic granulocytes in BALF, compared to unsensitized and unprovoked control animals, was noted. Twenty-four hours after provocation, there was also an elevation of ET-LI concentration and content of neutrophils. During the first day post-challenge, the ET-LI values were moderately correlated to the eosinophil levels. One week after challenge, the ET-LI level and the neutrophil count did not differ from corresponding values in control animals whereas the number of eosinophils remained elevated. Pretreatment with dexamethasone before the second allergen challenge did not consistently affect the parameters studied during the first 24 h. Bronchoconstriction induced by carbachol aerosol affected significantly neither the ET-LI concentration nor the number of inflammatory cells in BALF. It is concluded that the allergen-induced inflammation in the guinea-pig airways causes an elevation in the ET-LI concentration in BALF and that this is moderately correlated to the influx of eosinophils during the first 24 h.

Metabolism of Big endothelin-1 (1-38) and (22-38) in the human circulation in relation to production of endothelin-1 (1-21).

Healthy male volunteers received intravenous infusions of Big endothelin (ET)-1 (1-38) or Big ET-1 (22-38). Blood samples were drawn from catheters in the brachial and pulmonary arteries and the hepatic, renal, jugular and deep forearm veins. The in vivo half-lives of circulating plasma Big ET-1 (1-38) were 6.6 +/- 0.3 min for the initial phase and 23 +/- 1.4 min for the late phase. The corresponding half-lives of Big ET-1 (22-38) were considerably shorter, being 0.9 +/- 0.03 min (P < 0.01) and 3.1 +/- 0.4 min (P < 0.01), respectively. This was concordant with the efficient regional clearance of Big ET-1 (22-38), which was most prominent in the forearm muscle (51 +/- 3%), liver (44 +/- 5%) and kidney (43 +/- 3%) and less pronounced in the lungs (14 +/- 2%) and brain (22 +/- 5%). Significant fractional extraction of Big ET-1 (1-38) was only found for the liver (30 +/- 2%) and kidney (44 +/- 3%). During the infusion of Big ET-1 (1-38) a positive veno-arterial gradient of ET-1-LI was noted only for the kidney, indicating production of ET-1. In conclusion, whereas Big ET-1 (22-38) is eliminated in skeletal muscle, splanchnic, renal, pulmonary and cerebral vascular beds, Big ET-1 (1-38) is extracted mainly in the renal and splanchnic vasculature. Furthermore, plasma half-life of Big ET-1 (1-38) is much longer than that of both ET-1 and Big ET-1 (22-38) in man. Thus, for investigation of the secretory activity of the ET-1-system measurements of Big ET-1 (1-38) levels may be a better approach.

Regulatory effects of aerosolized budesonide and adrenalectomy on the lung content of endothelin-1 in the rat.

This study was designed to investigate the effect of inflammation and glucocorticosteroids (GCS) on the content of endothelin-1-like immunoreactivity (ET-LI) in the rat lung. Following intratracheal instillation of Sephadex beads, which induces a long-lasting inflammation in the lung, there was an increase in the lung content of ET-LI measured by RIA. This increase was abolished by locally administered aerosolized budesonide at doses that had only minor systemic effects (measured as a reduction in body weight). In a second series of experiments, rats were subjected to surgical adrenalectomy in order to reduce the levels of endogenous GCS. This procedure elevated the ET-LI levels in the lungs. In contrast, neither adrenalectomy nor high doses of budesonide administered systemically affected the concentration of ET-LI in the kidney. It is concluded that the lung ET levels are elevated in inflammatory conditions and that this increase is highly sensitive to locally administered GCS. Endogenous GCS may, directly or indirectly, play a role in the regulation of lung ET content but there seems to be no general GCS effect on basal tissue levels of ET.

Local overflow and enhanced tissue content of endothelin following myocardial ischaemia and reperfusion in the pig: modulation by L-arginine.

OBJECTIVE: The local myocardial overflow and tissue content of endothelin-like immunoreactivity (ET-LI) during ischaemia and reperfusion as well as the coronary vascular effects of endothelin were characterised in anaesthetised pigs. METHODS: Ischaemia was induced by ligation of the left anterior descending coronary artery for 45 min followed by 4 h of reperfusion. ET-LI was analysed in plasma from the anterior interventricular coronary vein and aorta for estimation of local overflow and in myocardial tissue. Endothelin analogues were given in the coronary artery for determination of local vascular effects. RESULTS: During reperfusion, but not during ischaemia, the veno-arterial concentration difference of ET-LI increased, resulting in a significantly increased overflow at between 10 and 120 min of reperfusion. The tissue concentration of ET-LI in the left ventricle was seven times higher in the ischaemic/reperfused area than in the non-ischaemic area: 161(SEM 30.5) v 25.3(3.8) fmol.g-1, P < 0.05. The increase in myocardial ET-LI was attenuated by 70% (P < 0.01) by coronary venous retroinfusion of the nitric oxide substrate L-arginine, whereas the overflow was unaffected. Chromatographic characterisation of the myocardial ET-LI showed that it was similar to endothelin-1. Intracoronary administration of endothelin-1, endothelin-3, and the endothelin ETB receptor agonist [Ala1,3,11,15]ET-1 evoked dose dependent coronary vasoconstriction, and reductions in left ventricular dP/dt and arterial blood pressure. Endothelin-1 was two times more potent than endothelin-3 and 10 times more potent than [Ala1,3,11,15]ET-1. CONCLUSIONS: Myocardial ischaemia/reperfusion evokes enhanced local overflow of ET-LI during the reperfusion period combined with an increased tissue concentration of ET-LI which is is attenuated by L-arginine. Endothelin evokes potent coronary vasoconstriction via activation of both ETA and ETB receptors.

Big ET-1 infusion in man causes renal ET-1 release, renal and splanchnic vasoconstriction, and increased mean arterial blood pressure.

OBJECTIVE: The aim was to study the vascular effects of big endothelin-1 (big ET-1) infusion and its possible conversion to ET-1. METHODS: Six healthy subjects were given an intravenous infusion of big ET-1 in a dose of 8 pmol.kg-1.min-1 for 20 min. Blood samples were taken before, during, and up to 3 h after the infusion from arterial, hepatic, and renal vein catheters for the determination of splanchnic and renal blood flows, as well as ET-1-like immunoreactivity (ET-1-LI) from these vascular beds. RESULTS: Intravenous infusion of big ET-1 was followed by a doubling of arterial ET-1-LI from 4.17(SEM 0.39) to 8.42(0.49) pmol.litre-1 (p < 0.001) and a significant increase in the renal release of ET-1-LI from 1.50(0.18) to 8.68(0.64) pmol.min-1 (p < 0.001) but no splanchnic release. Big ET-1 infusion also caused a decrease in heart rate from 57(4) to 45(3) beats.min-1 (p < 0.001) and an increase in mean arterial pressure from 86(1.3) to 106(3.2) mm Hg (p < 0.001), which lasted for at least 2 h. Renal blood flow fell from 1.38(0.06) to 0.83(0.04) litre.min-1 (p < 0.001) while splanchnic blood flow fell from 1.34(0.11) to 0.83(0.05) litre.min-1 (p < 0.001). CONCLUSIONS: Big ET-1 infusion causes a drop in heart rate, an increase in mean arterial pressure and decreases in splanchnic and renal blood flows. Arterial plasma ET-1 levels doubled and big ET-1 infusion also induced a significantly increased renal, but not splanchnic, release of ET-1-LI, suggesting a unique renal handling of circulating big ET-1. When the results of the infusion of big ET-1 are compared with our previous experiments using ET-1 infusion, more marked haemodynamic changes (as reflected in the increase in mean arterial pressure, the drop in heart rate, and the duration of renal vasoconstriction) are seen despite lower arterial plasma ET-1-LI levels.

Renal tissue endothelin in long-term complete ureteric obstruction in the young rat.

Complete obstruction of one ureter was created in 3-week-old weanling rats. The endothelin concentration in the renal tissue was measured by radioimmunoassay. In the obstructed kidney, a substantial increase was observed, after 1 week +90%, after 2 weeks +55%, and after 4 weeks +145% compared to the control rat kidneys. The endothelin-1/endothelin-3 ratio was found to be considerably raised, indicating a predominance of the vasoconstrictor effects of the--with reference to vasoactivity--bi-potential endothelin. Its contribution to vasoconstriction and to glomerular destruction in obstructive nephropathy is discussed.