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Query: UMLS:C0432222 (SEM)
 47,337 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Milk samples from lactating women (n = 24) were examined for atrial natriuretic peptide (ANP) and endothelin-1 (ET-1) content throughout the first 3 months postpartum. Samples were collected at the beginning (foremilk) and towards the end (hindmilk) of nursing. ANP was detected in the milk samples. A value of 9.4 +/- 1.8 pmol/l (mean +/- SEM) was observed on the third day postpartum. No significant variations in concentrations were observed during the 3 months examined. Foremilk and hindmilk ANP concentrations were also similar. ET-1, as previously reported, is present in the milk of lactating women. According to our observations, the concentration of ET-1 varies during the first 3 postpartum months. The highest concentrations were observed on the third day (10.2 +/- 1.8 pmol/l) of lactation, decreasing to 4.5 +/- 0.8 pmol/l after 1 week (p < 0.05) and to 2.0 +/- 0.3 pmol/l, at 1 month postpartum (p < 0.05), this level being maintained for up to 3 months postpartum. Foremilk samples on the third day postpartum contained significantly higher concentrations of ET-1, compared to hindmilk samples (10.2 +/- 1.8 vs 7.7 +/- 1.2 pmol/l, p < 0.05). The stable levels of ANP and the initial high and subsequently decreasing levels of ET-1 in human milk, during the first 3 months postpartum, suggest that these peptides might be of importance either in the lactating mammary gland or in the suckling newborn.
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PMID:Atrial natriuretic peptide and endothelin concentrations in human milk during postpartum lactation. 930 55

Elevations in circulating levels of both endothelin-1 (ET-1) and insulin are found in coronary heart disease and chronic heart failure. Although several studies have shown that insulin can stimulate ET-1 release from endothelial cell cultures, in vivo studies have yielded equivocal results. We sought to determine whether endogenous insulin at physiological concentrations leads to alterations in venous plasma ET-1 levels in healthy subjects. In addition, we investigated the effects of physiological and supraphysiological doses of insulin on the release of ET-1 from human umbilical vein endothelial cells (HUVECs) in vitro. In the in vitro experiment, ET-1 and insulin levels were measured during an intravenous glucose tolerance test (IVGTT) in 10 healthy subjects. In the in vitro experiment, HUVECs were incubated in the absence of serum and with different concentrations of insulin (25 pmol/L to 1 mumol/L) for 4 hours before measurement of secreted ET-1. The in vivo study showed no significant alterations in venous plasma ET-1 levels during IVGTTs (maximum plasma insulin, 616.9 +/- 147.0 pmol/L [mean +/- SEM]). In the in vitro experiment, increases in ET-1 release were observed under serum-free conditions at 100 pmol/L (physiological) and 1 mumol/L (supraphysiological) insulin (ET-1, 22.4% and 46.4% higher than control cultures, respectively, both P < .05). Our results show that insulin at physiological concentrations does not alter plasma ET-1 levels in healthy individuals, but does stimulate its secretion from vascular endothelial cells in vitro. This may have implications for the study of elevated ET-1 in hyperinsulinemic states.
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PMID:Physiological hyperinsulinemia is not associated with alterations in venous plasma levels of endothelin-1 in healthy individuals. 932 95

Because changes in extracellular volume during dialysis cause reflex neurohonnonal changes that may influence parathyroid hormone (PTH) release independently of calcium, the influence of isotonic volume depletion (by isolated ultrafiltration) and central hypovolemia (70 degrees tilt) on serum PTH1-84 was studied in 16 hemodialysis patients. Tilting was performed in volume depleted state, i.e., immediately after hemodialysis. In the control study, patients underwent sham ultrafiltration (UF = 0) and after dialysis maintained the supine position for the same length of time they remained in the tilt position in the active experiment. Isolated ultrafiltration (-2.3 +/- SEM 0.3 L) caused a 21% fall in mean arterial pressure (from 101 +/- 6 to 80 +/- 6 mmHg, P < 0.01), a fall that was accompanied by a marked increase in plasma catecholamine levels (norepinephrine P < 0.001, epinephrine P < 0.025), in plasma renin activity (P < 0.001) and in plasma arginine vasopressin (P < O.001). Atrial natriuretic factor showed a slight reduction, whereas the plasma endothelin-1 level did not change. Serum Ca showed the expected, hemoconcentration-dependent rise (from 4.1 +/- 0.1 to 4.4 +/- 0.1 meq/L, P < 0.01). Interestingly, UF caused a marked rise in plasma PTH1-84 concentration (from 252 +/- 62 to 335 +/- 72 pg/ml, P < 0.01). UF-induced changes in serum PTH1-84 were related to norepinephrine changes (r = 0.57) as well as to plasma renin activity (r = 0.50). After hemodialysis, tilting induced a pronounced rise in serum PTH1-84 (from 102 +/- 29 to 200 +/- 55 pg/ml), and these changes were slightly related to plasma epinephrine (r = 0.49) but independent of other parameters. In the control experiment, neither sham UF nor recumbency modified serum PTH. In hemodialysis patients, serum PTH is sensitive to changes in extracellular and central blood volume of magnitude sufficient to decrease arterial pressure. Avoiding marked volume stimuli might help to refine the interpretation of the Ca/PTH curves during hemodialysis in these patients.
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PMID:The influence of volume depletion and central hypovolemia on the plasma concentration of parathyroid hormone in dialysis patients. 933 86

1. There is an increase in circulating levels of vasoconstrictive hormones and an alteration in baroreceptor responsiveness with aging. The role of changes in endothelium-dependent and -independent vasoconstrictive hormones in relation to age and gender, with simultaneous assessment of autonomic balance in response to head-up tilt, has been incompletely studied. 2. Sixteen young [25 +/- 3 years (mean +/- SEM)] and 16 older normal volunteers (68 +/- 7 years) underwent a 30 min head-up tilt test at 60 degrees. Haemodynamics were measured every 5 min and blood samples for neurohormone measurement were drawn at baseline, 5, 10, 15 and 30 min into the test. Heart rate variability was analysed in 5 min segments at the baseline, and during the test. The younger subjects exhibited a greater increase in heart rate and diastolic blood pressure, despite lower absolute levels of noradrenaline (norepinephrine) and endothelin-1. Analysis of heart rate variability yielded a decrease in both high- and low-frequency bands in the aged; power at low-frequency decreased only in the young subjects. The age-related differences in blood pressure and noradrenaline levels were markedly attenuated in the female subjects. In addition, endothelin-1 levels and power spectral measurements at low frequency were the lowest in younger females throughout the tilt. 3. Despite attenuated cardiovascular response to tilt, both systemic adrenergic 'drive' and endothelin-1 levels increase in parallel with aging. Thus, endothelium-dependent and -independent vasoconstrictive hormone levels increase with age in the resting state and in response to neurohumoral stimulation in humans.
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PMID:Age- and gender-related changes in endothelin and catecholamine release, and in autonomic balance in response to head-up tilt. 940 22

The neurohumoral events associated with neurocardiogenic syncope remain unclear. The simultaneous assessment of changes in endothelium-dependent and independent hormones and in autonomic balance in patients with tilt-induced syncope has been incompletely studied. Forty-six healthy subjects aged between 21 and 83 years (mean +/- SEM 47 +/- 3) underwent a 30-minute head-up tilt test at 60 degrees. Fourteen subjects (10 females and 4 male subjects) exhibited syncope at 16 +/- 2 minutes into the tilt. Hemodynamics were recorded every 5 minutes and blood samples for the measure of catecholamines, endothelin-1 (ET-1), and angiotensin-II (AT-II), were drawn at baseline, and 5, 10, 15, and 30 minutes into the tilt and immediately before syncope. Heart rate variability was analyzed by 5-minute segments during the test. Both catecholamines and ET-1 levels increased consistently in response to head-up tilt in subjects able to tolerate the test. Epinephrine increased to a greater extent before syncope. In contrast, ET-1 failed to increase at any time during the tilt and just before syncope. AT-II increased at 30 minutes into the tilt only in the control group. Finally, power in high-frequency bands decreased less in the group with syncope. Thus, compared with subjects able to tolerate a head-up tilt test, patients with syncope exhibit a greater increase in adrenomedullary activation, no significant increase in ET-1 levels, and a blunting in the decrease of vagal tone before syncope. The lack of increase in ET-1 during tilt may play a role in the inability to support orthostatic stress.
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PMID:Impaired endothelin-1 release in tilt-induced syncope. 948 37

Limited information is available for humans on whether blood viscosity affects total peripheral resistance and, hence, blood pressure. Our study was aimed at assessing the effects of acute changes in blood viscosity on both clinic and 24-hour ambulatory blood pressure (BP) values. In 22 normotensive and hypertensive patients with polycythemia, clinic and 24-hour ambulatory BPs were measured before and 7 to 10 days after isovolumic hemodilution; this was performed through the withdrawal of 400 to 700 mL of blood, with concomitant infusion of an equivalent volume of saline-albumin solution. Hematocrit, plasma renin activity, plasma endothelin-1, right atrial diameter (echocardiography), and blood viscosity were measured under both conditions. Plasma renin activity and right atrial diameter were used as indirect markers of blood volume changes. Plasma endothelin-1 was used to obtain information on a vasomotor substance possibly stimulated by our intervention, which could counteract vasomotor effects. Isovolumic hemodilution reduced hematocrit from 0.53+/-0.05 to 0.49+/-0.05 (P<.01). Plasma renin activity, plasma endothelin-1 and right atrial diameter were unchanged. Clinic blood pressure was reduced by hemodilution (systolic, 144.3+/-5.4 to 136.0+/-3.9 mm Hg[mean+/-SEM]; diastolic, 87.0+/-2.8 to 82.1+/-2.6 mm Hg, P<.05 for both) and a reduction was observed also for 24-hour average ABP (systolic, 133.6+/-2.9 to 129.5+/-2.7 mm Hg; diastolic, 80.0+/-2.0 to 77.3+/-1.7 mm Hg, P<.05 for both). The reduction was consistent in hypertensive patients (n = 12), whereas in normotensive patients (n = 10) it was small and not significant. Both clinic and 24-hour average heart rates were unaffected by the hemodilution. Thus, in polycythemia, reduction in blood viscosity without changing blood volume causes a significant fall in both clinic and 24-hour ambulatory BPs; this is particularly true when, as can often happen, blood pressure is elevated. This emphasizes the importance this variable may have in the determination of blood pressure and the potential therapeutic value of its correction when altered.
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PMID:Hemodilution reduces clinic and ambulatory blood pressure in polycythemic patients. 949 71

Humans genetically predisposed to hypertension tend to develop at a prehypertensive stage subtle metabolic and hormonal dysregulations, and certain of these could potentially be angiotensin II dependent. Therefore the aim of this study was to investigate the effects of the angiotensin II-receptor antagonist losartan on insulin sensitivity, lipid profile, and plasma endothelin-1 (ET-1) levels in normotensive offspring of hypertensive parents with a randomized, double-blind, placebo- controlled, crossover design. Insulin sensitivity index (SI), determined by the Minimal Model Method of Bergman, fasting plasma insulin and glucose concentrations, serum total and HDL cholesterol, serum triglycerides, and plasma ET-1 levels were assessed in 19 young (26.2 +/- 0.7 years, mean +/- SEM), healthy, lean [body mass index (BMI), 22.6 +/- 0.7 kg/m2] normotensive male offspring of essential hypertensive parents after 14 days of losartan, 50 mg, and 14 days of placebo, respectively. Compared with placebo, losartan administration did not significantly modify SI (12.2 +/- 1.7 vs. 12.7 +/- 1.5 x 10(-4)/min/microU/ml on placebo), fasting plasma insulin and glucose, as well as the areas under the insulin and glucose curves. Plasma ET-1 levels also did not differ significantly between the placebo and losartan administration phases (1.1 +/- 0.06 vs. 1.2 +/- 0.06 pg/ml). However, serum total cholesterol and triglycerides decreased significantly with losartan treatment (3.8 +/- 0.2 vs. 4.1 +/- 0.2 mM and 0.9 +/- 0.1 vs. 1.1 +/- 0.1 mM, respectively; p < 0.01). Body weight, BMI, heart rate (HR), blood pressure (BP), and 24-h urinary sodium, potassium, and creatinine values were stable throughout the study. These findings demonstrate that angiotensin II-receptor blockade with losartan, administered in the therapeutic dose of 50 mg daily, does not alter insulin sensitivity determined by the Minimal Model Method of Bergman and does not affect ET-1 in normotensive offspring of essential hypertensive parents. The normal insulin sensitivity in the subjects studied might explain why losartan did not improve it. However, losartan significantly reduced serum total cholesterol and total triglyceride levels.
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PMID:Effects of angiotensin II-receptor blockade with losartan on insulin sensitivity, lipid profile, and endothelin in normotensive offspring of hypertensive parents. 955 7

Our aim was to localize endothelin-converting enzyme (ECE) in human saphenous vein grafts and to quantify enzymic activity in cultured human endothelial and smooth-muscle cells. Immunoreactive ECE localized to the endothelium and infiltrating macrophages in vein grafts, but little or no immunoreactivity was detected within the media or proliferated smooth muscle of the occlusive lesion. Cultures of human umbilical vein endothelial cells were incubated with big endothelin-1 (ET-1) (10 nM) to measure extracellular conversion. After 2 h the concentration of mature peptide in the medium was increased by 162.7 +/- 21.6 pM (n = 3 +/- SEM) above basal. Permeabilization of the cells increased conversion to 1077.9 +/- 52.8 pM, suggesting that about 85% of ECE activity was located intracellularly. In both cases, activity was inhibited by phosphoramidon but not by thiorphan. In contrast, conversion of big ET-3 (10 nM) under the same conditions was not detected in either intact or permeabilized cells after 2 h. Big ET-3 and big ET-1 were converted by a phosphoramidon-sensitive/thiorphan-insensitive enzyme on the surface of confluent cultures of human umbilical vein smooth-muscle cells, with concentrations of the corresponding mature peptides increasing by 99.5 +/- 14.5 pM and 222.2 +/- 11.6 pM, respectively. These results suggest that smooth-muscle cells could be responsible for the synthesis of ET-3 present in plasma and for additional processing of big ET-1 released by endothelial cells.
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PMID:Endothelin-converting enzyme in the human vasculature: evidence for differential conversion of big endothelin-3 by endothelial and smooth-muscle cells. 959 83

Choroid plexus carcinoma is a rare neoplasm derived from the epithelium of the choroid plexus. The production and secretion of endothelin-1 (ET-1) by cultured human choroid plexus carcinoma cells were studied by radioimmunoassay and Northern blot analysis. Immunoreactive (IR)-ET was detected in the culture medium (2.78 +/- 0.12 fmol/10(5) cells/24 h; n = 5; mean +/- SEM) but not in the unconditioned medium. Reverse-phase high-performance liquid chromatography of the extract of the culture medium showed a single peak eluting in the position of ET-1. Treatment with tumor necrosis factor-alpha (TNF-alpha), interleukin-1 beta (IL-1 beta) or a combination of interferon-gamma (IFN-gamma), TNF-alpha, and IL-1 beta caused significant increases in the IR-ET levels in the culture medium. Northern blot analysis of total RNA showed the expression of ET-1 mRNA in choroid plexus carcinoma cells. The expression levels of ET-1 mRNA were increased by treatment with a combination of IFN-gamma, TNF-alpha, and IL-1 beta. The present study has shown the production and secretion of ET-1 by cultured human choroid plexus carcinoma cells and suggests the possibility that ET-1 formation is related to the pathophysiology of this tumor.
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PMID:Production and secretion of endothelin-1 by cultured choroid plexus carcinoma cells. 959 84

Mammalian ovaries and testes contain various intragonadal peptides necessary to control gonadal function. Effects of aging and sex on total plasma and ovarian or testicular endothelin-1 (ET-1) levels were studied in female and male rats aged 4-140 days. At 2 weeks, plasma ET-1 levels were 2.69 +/- 0.09 and 2.41 +/- 0.03 pg/ml (mean +/- SEM; n = 10) in the female and male, respectively. After a temporary decrease, mean ET-1 concentrations increased at 10 weeks and again decreased at 20 weeks in the female, thereafter revealing a plateau, whereas the ET-1 concentrations gradually decreased in the male. In adult females, plasma ET-1 levels were 3.7-fold higher than male levels. Ovarian ET-1 levels gradually increased after birth to 2 weeks, then decreased, and again increased at 3 weeks. Thereafter they gradually decreased, showing a plateau after 10 weeks. In contrast, testicular ET-1 levels gradually decreased after birth. This difference is parallel to but much larger than the sex difference in ovarian or testicular ET-1. Gonadal ET-1 showed a very different ontogeny.
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PMID:Changes with age and sex in levels of plasma and ovarian or testicular endothelin-1 in rats. 959 32


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