缺氧时心肌血流量的变化及一氧化氮和内皮素-1的调节作用

目的探讨一氧化氮和内皮素-1在缺氧时对心肌血流量的调节作用。方法大鼠随机分为平原组和急性缺氧组,用99mTc标记蟾蜍红细胞测定心肌血流量,用Gess法和放免法分别测量血浆和心肌NO2-、内皮素-1（endothelin-1,ET-1）含量,用双波长分光光度法测量一氧化氮氧合酶（nitric oxide synthase,NOS）活性。结果急性缺氧导致左右心室心肌血流量、血浆和心肌血NO2-、ET-1含量、NOS活性明显增高（P〈0.05）,左右心室心肌血管阻力和心肌ET-1/NO2-比值明显下降（P〈0.05）,血球压积（Hct）及心室重量指数无明显变化。结论急性缺氧时,左右心室心肌血流量增加,ET-1/NO参与了急性缺氧时心肌血流量的调节,以NO的扩血管作用为主。     

Exogenous endothelin-1 causes peripheral insulin resistance in healthy humans

In states of insulin resistance, increased plasma levels of endothelin-1 and a disturbed vascular reactivity have been reported. In order to investigate the effects of endothelin-1 on peripheral insulin sensitivity and the vasoactive interactions between insulin and endothelin-1, six healthy subjects were studied on two different occasions with the euglycaemic hyperinsulinaemic clamp technique combined with an intravenous infusion of either endothelin-1 (4 pmol kg^?1 min^?1) or 0.9% sodium chloride. During the endothelin-1 infusion, arterial plasma endothelin-1 levels rose 10-fold. The endothelin-1 infusion reduced insulin sensitivity as demonstrated by a 31 ± 7% decrease in whole-body glucose uptake (P < 0.05) and a 26 ± 11% fall in leg glucose uptake (P < 0.05) compared with the control protocol. During the state of hyperinsulinaemia, exogenous endothelin-1 increased mean arterial blood pressure by 8 ± 1% (P < 0.05) and decreased splanchnic and renal blood flow by 30 ± 6% (P < 0.001) and 20 ± 4% (P < 0.001), respectively. However, the endothelin-1 infusion did not lower skeletal muscle blood flow measured as leg and forearm blood flow. In summary, exogenous endothelin-1 induced insulin resistance in healthy humans by reducing insulin-dependent glucose uptake in skeletal muscle without decreasing skeletal muscle blood flow. Furthermore, endothelin-1 also preserved its vasoactive potency in the presence of hyperinsulinaemia.     

Vascular effects of endothelin-1 in the cat; modification by indomethacin and l-NAME

Intravenous infusion of endothelin-1 (ET-1) in the cat, 60 pmol × kg body wt^-1x min^-1for 5 min, induced an increase in mean arterial blood pressure (MAP) of 41.3 ± 4.8 mmHg (n= 6; P < 0.001). Blood flow, as determined with radioactive microspheres, was reduced in many tissues. Reductions by 70–80% were observed in the choroid plexus, pineal and pituitary glands. Total cerebral blood flow was reduced by 18–23%. Pre-treatment with indomethacin or a combination of indomethacin and l -NAME caused vasoconstriction in many tissues and modified the responses to ET-1 in a variable way, suggesting that normally, ET-1 tends to release arachidonic acid metabolites and nitric oxide with great variations between different tissues. Intracerebroventricular infusion (i.c.v.) of ET-1, 10 pmol × kg body wt^-1x min^-1, caused an increase in MAP of 79 ± 11 mmHg (n= 6; P < 0.001). Regional blood flow in the medulla oblongata, medulla spinalis, choroid plexus, pineal and pituitary glands was reduced by 60–80%. Heart rate, cardiac output and coronary blood flow were significantly increased after 30 min i.c.v. infusion, indicating an activation of the heart, most probably as part of a central ischaemic response. Our results indicate that in many tissues the vasoconstrictive effect of ET-1 is influenced by indomethacin- and l -NAME-sensitive vasodilator mechanisms that are activated by the peptide. In the CNS, there may be marked effects on regional blood flow after i.c.v. infusion.     

Immunoreactive endothelin-1, endothelin-2 and big endothelin-1 in follicular fluids of women undergoing ovulation induction for in-vitro fertilization

Endothelin-like immunoreactivity specific for endothelin-1 (ET-1),endothelin-2 (ET-2) or big endothelin-1 (big ET-1) was measured,using commercially available radioimmuno-assay kits, in follicularfluid collected at the time of oocyte aspiration from 36 womenundergoing ovulation induction by human menopausal gonadotrophin(HMG). The relation-ship of ET concentrations to HMG dose, peakserum oestra—-diol concentration, the number and sizeof follicles (by ultrasound), the number of retrieved oocytesand the fertilization rate per retrieved oocyte were studied.Overall, 94% of follicular fluid samples were positive for ET-1,92% were positive for ET-2, and 100% were positive for big ET-1.Mean ET-1, ET-2 and big ET-1 concentrations were 17.23±12.20,32.42± 14.32 and 34.55± 16.34 pg/ml respectively.Endo-thelin-like immunoreactivity in follicular fluid sampleswas found in an order of ET-1<ET-2< big ET-1. There wasa highly significant positive correlation (r=0.8711, P=0.0001,n=32) between follicular ET-1 and ET-2 concentrations. No significantcorrelation of follicular big ET-1 was established either withET-1 or ET-2. However, big ET-1 was found to be negatively correlatedwith number of oocytes (P=0.03) and number of follicles (P=0.04).Control plasma ET-1 and follicular ET-1 were not significantlydifferent. There was no significant correlation between ET concentrationsand any of the other studied parameters. The results demonstratedthat immunoreactive ET-1, ET-2 and big ET-1 exist in human follicularfluid collected at the time of oocytes retrieval for in-vitrofertilization and may be involved in the regulation of reproductivefunction. The clinical significance and physiological role offollicular fluid ET deserve further studies.     

Modulation of systolic and diastolic function by endothelin-1: relation to coronary flow

Different conclusions have been reached with regard to the effect of endothelin (ET-1) on cardiac contractility. We examined systolic and diastolic function in response to constant known concentrations of ET-1 with or without ET-1 induced reductions in coronary flow (CF). Rat hearts (n= 21) were buffer-perfused using constant coronary flow (cCF) or constant perfusion pressure (cPP). Left ventricular function was assessed isovolumically. Addition of ET-1 (10^-9 M) in the cCF group caused a gradual increase in PP from 61 ± 2 to 165±6mmHg (mean±SE) (P < 0.01). Within 10 min left ventricular systolic pressure (LVSP) increased from 111 ± 2 to a maximum of 134±4mmHg (P < 0.01) and [L\dP/dt] increased from 1640 ± 81 to a maximum of 2020 ± 92 mmHg s“¹ (P < 0.01). After 15 min left ventricular end diastolic pressure (LVEDP), a measure of diastolic stiffness (DS), also increased. With ET-1 (10 ⁸ M), similar haemodynamic alterations appeared more rapidly. In the cPP group, ET-1 (10”⁹ M) caused a sharp decrease in CF and LVSP fell from 115 ± 8 to 62±12 mmHg at 10 min (P < 0.001). Systolic function remained stable at a reduced level for 1 h. DS did not change. Thus, ET-1 possesses positive inotropic effects and increases diastolic stiffness. Both effects may be masked by vasoconstriction-induced ischaemia.     

Augmented expression of endothelin-1, endothelin-3 and the endothelin-B receptor in breast carcinoma

AIMS: Endothelins (ETs) are peptides expressed in many tumours which may stimulate angiogenesis and desmoplasia. Because ETs have not been extensively studied mammary neoplasia, we assessed ET protein and mRNA expression and receptor mRNA expression in normal and neoplastic breast tissues. METHODS AND RESULTS: Tissues from five normal breasts, six fibroadenomas, seven ductal carcinomas in situ (DCIS) and 25 invasive carcinomas were stained with anti-ET-1 and anti-ET-3 antibodies and analysed using a grading system. ET-1, ET-3, ETA and ETB mRNA expression was assessed by quantitative RT-PCR from eight carcinomas and five normals. Weak staining for ET-1 and ET-3 was detected in all normals. Moderate to strong staining was seen in 72% and 64% of carcinomas for ET-1 and ET-3, respectively. Most fibroadenomas showed weak positivity for ET-1 (83%) and ET-3 (67%). ET-1 and ET-3 mRNA levels were upregulated in carcinomas compared with normal breast. No ETA mRNA was not detected in any tissue. ETB mRNA was detected in normal breast and was increased in carcinomas. CONCLUSION: These results suggest that the ET system is altered in breast carcinomas and this may be of importance in the progression from in-situ to invasive carcinoma.     

Pregnancy: Oxygen promotes contraction by endothelin-1 in human umbilical artery

The influence of oxygen on the contractile response to endothelin-1in the human umbilical artery was investigated in vitro. Segmentsof human umbilical artery were suspended in organ baths to recordthe circular motor activity induced by endothelin-1 at a pO₂of 12 kPascal (kPa) or 45 kPa. Endothelin-1 induced a concentration-dependentcontraction which was significantly larger at 45 kPa O₂ comparedwith the contractile response at 12 kPa O₂.     

Splanchnic and renal vasoconstrictor and metabolic responses to neuropeptide Y in resting and exercising man

The local clearance of neuropeptide Y (NPY) and whether NPY influences splanchnic and renal metabolism in man have not been investigated previously. The influence of NPY on splanchnic and renal blood flows at physiologically elevated levels has also not been investigated. The effects of a 40-min constant NPY infusion (3 pmol kg^-1 min^-1) at rest and during 130 min of exercise (50% of Vo_2max) were studied in six healthy subjects and compared with resting and exercising subjects receiving no NPY. Blood samples were drawn from arterial, hepatic and renal vein catheters for the determination of blood flows (indicators: cardiogreen and paraaminohippuric acid [PAH]), NPY, catecholamines, glucose, lactate and glycerol. NPY infusion was accompanied by: (1) significant fractional extraction of NPY-like immunoreactivity (NPY-Li) by splanchnic tissues at rest (58±5%) and during exercise (53±6%), while no arterial–venous differences could be detected across the kidney; (2) a reduction in splanchnic and renal blood flows of up to 18 and 13% respectively (P < 0.01–0.001) at rest without any additional changes during exercise; and (3) metabolic changes as reflected in: (a) a more marked fall in arterial glucose during exercise compared to the reference group (P < 0.05); (b) a 35% lower splanchnic glucose release (P < 0.01) during exercise due to diminished glycogenolysis (P < 0.01); and (c) a lower arterial lactate level (18%P < 0.05) together with unchanged splanchnic lactate uptake during exercise, suggesting reduced lactate production by extrahepatic tissues. The disappearance of plasma NPY-Li after the infusions was biphasic with two similar half-lives at rest (4 and 39 min) and during exercise (3 and 43 min).     

Increased renal glomerular endothelin-1 release in gentamicin-induced nephrotoxicity

Gentamicin-induced acute renal failure is characterized by a decrease in renal plasma flow and creatinine clearance. Endothelins (ET) are potent renal vasoconstrictors. The aim of this work is to assess the role of ET-1 in gentamicin-induced renal failure. Renal glomerular release of ET-1 was measured in rats with gentamicin-induced nephrotoxicity (100 mg/kg/day, s.c. for 2, 4 or 6 days). Glomeruli were isolated and incubated for 24 h in RPMI-1640. Glomerular supernatant and plasma concentration of ET-1 were measured by RIA. Renal failure was assessed by insulin, para-aminohippuric and creatinine clearance and histological studies. Gentamicin induced a dose number-dependent increase in plasma creatinine and a decrease in creatinine clearance. This was accompanied by a marked decrease in inulin and para-aminohippuric acid clearance, as well as by a marked tubular necrosis, without alterations in glomerular structures. Plasma ET-1 concentration and glomerular ET-1 release were also increased in gentamicin-treated rats. When 10-5 M gentamicin was added to control glomeruli, ET-1 production was not modified (36.4 +/- 2.2 vs. 35.2 +/- 1.7 pg/ml/24 h). All these results suggest that elevated ET-1 plasma levels and increased glomerular release of ET-1 could mediate, at least in part, the decrease in glomerular filtration rate observed in gentamicin-induced ARF.     

Arrhythmogenic effects of endothelin-1 under conditions of NO-synthase blockade with L-NAME in NMRI mice

Arrythmogenic effects of endothelin-1 were studied in NMRI mice under conditions of NO-synthase blockade with N-nitro-L-arginine methyl ester. Intravenous injection of endothelin-1 increased heart rate variability in awake mice. NO-synthase blockade potentiated the arrythmogenic effects of endothelin-1. In narcotized animals the arrythmogenic effect of endothelin-1 was not observed and was considerably weakened under conditions of NO-synthase blockade. Arrhythmia was paralleled by atrioventricular block and lengthening of the ST segment.     

Effect of leukotriene LTC4 on the coronary vascular bed and myocardial contractility

Department of Experimental Cardiology, A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 111, No. 2, pp. 120–123, February, 1991.     

阿托伐他汀对不稳定心绞痛患者内皮素-1和一氧化氮的影响

目的:观察阿托伐他汀治疗不稳定型心绞痛疗效及其对内皮素-1(endothelin-1,ET-1)和一氧化氮(nitric oxide,NO)的影响.方法:将不稳定型心绞痛患者随机分为治疗组(n=45)和对照组(n=45),2组均给予同样的常规治疗,治疗组加用阿托伐他汀,均治疗2个月后观察治疗前后心绞痛疗效,检测ET-1...     

The association of endothelin-1 gene polymorphism and its plasma levels with hypertension and coronary atherosclerosis

IntroductionEndothelin-1 (ET-1) is the most potent among all vasoconstrictors, and its association with cardiovascular diseases has been reported before. Our aim was to investigate the association of ET-1 plasma level and its gene polymorphisms (rs5370 and rs10478694) with hypertension and coronary atherosclerosis (CA).Material and methodsThis study was carried out on 128 women and 132 men, who were divided into 4 groups: hypertensive without atherosclerosis (H+A–); hypertensive with atherosclerosis (H+A+); non-hypertensive with atherosclerosis (H–A+); and non-hypertensive without atherosclerosis (control group). Endothelin-1 plasma levels were measured by ELISA, and gene polymorphisms were detected by polymerase chain reaction – restriction fragment length polymorphism (PCR-RFLP) methods. Coronary artery diseases (CAD) were then defined based on angiography data.ResultsThe ET-1 plasma level was significantly higher in the H+A+ group in comparison with the other groups, especially H+A–. Comparing people with CA and those without it, the highest frequency level of the T allele of rs5370 was found in people with CA. Significantly higher frequencies of the 3A allele were detected in hypertensive patients in comparison with non-hypertensive individuals, when analyzing rs10478694.ConclusionsEndothelin-1 plasma level shows a direct association with the risk of CA development. The T allele of rs5370 can be regarded as a risk factor for CA development. The 3A allele of rs10478694 can be associated with the risk of hypertension; therefore, it can be concluded that ET-1 and its gene polymorphisms play an important role in CA development and hypertension observed in the south-eastern populations of Iran.     

PET tracers and techniques for measuring myocardial blood flow in patients with coronary artery disease

Assessment of the relative distribution of myocardial flow with myocardial perfusion imaging （MPI） is meth- odologically limited to predict the presence or absence of flow-limited coronary artery disease （CAD）. This limi- tation may often occur, when obstructive lesions involve multiple epicardial coronary arteries or disease-related disturbances of the coronary circulation coexist at the microvascular level. Non-invasive assessment of myocar- dial blood flow in absolute units with position emission tomography （PET） has been positioned as the solution to improve CAD diagnosis and prediction of patient outcomes associated with risks for cardiac events. This article reviews technical and clinical aspects of myocardial blood flow quantitation with PET and discusses the practical consideration of this approach toward worldwide clinical utilization.     

Physiological concentrations of endothelin-1 cause only coronary vasodilatation in anesthetized rats

Various concentrations of the peptide endothelin-1 were tested for their effect on coronary vascular resistance in anesthetized rats. Intracoronary infusion of this peptide over 4 min in a total dose that gave rise to blood concentrations of 0.002–0.003 or 0.2–0.3 fmol/ml elicited only a decrease in the estimated coronary vascular resistance. It is suggested that only supraphysiological doses of endothelin are likely to exert a powerful vasoconstrictive effect on coronary vessels and cause myocardial ischemia. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 120, N ^o 7, pp. 16–19, July, 1995 Presented by I. P. Ashmarin. Member of the Russian Academy of Medical Sciences     

冠状动脉微栓塞后冠脉血流储备及心肌血流量的变化及其机制

目的:经导管建立冠状动脉微栓塞模型,测定微栓塞后冠脉血流储备及心肌血流量的变化情况,并探讨其机制。方法:12只小型猪,通过导管方法建立急性冠脉微栓塞模型,观察急性期（基础、微栓塞后2 h、6 h）及慢性期（基础、微栓塞后1周）冠脉血流储备和心肌血流量的变化情况,并测定血清中内皮素-1（ET-1）浓度变化。结果:急性期冠脉微栓塞后冠脉血流储备在基础、微栓塞后2 h、6 h分别为2.10±0.60、1.40±0.10及1.10±0.10（微栓塞后2 h及6 h与基础相比,均P<0.01）,慢性期实验中,冠脉血流储备在微栓塞前及微栓塞后1周分别为2.03±0.43及1.58±0.22（微栓塞后1周与基础相比,P<0.05）。但前内侧和后内侧心肌血流量以及它们的比值在微栓塞后没有显著变化。测定血清ET-1浓度显示微栓塞后2 h开始升高,但只有微栓塞后6 h较基础有明显增加(P<0.05),微栓塞后6 h及1周心脏标本NBT染色均未见梗死灶。结论:冠脉微栓塞后冠脉血流储备呈现先下降后恢复的趋势,这种变化与内皮功能变化一致,冠脉血流储备和心肌血流量变化不同步。     

哮喘豚鼠气道上皮细胞原癌基因c-fos活化与ET-1释放相关性的研究

目的：探讨哮喘豚鼠发作时气道上皮细胞原癌基因c-fos的活化与上皮细胞释放内皮素－1（ET－1）的相关性。方法：将豚鼠随机分为哮喘组，地塞米松组和正常对照组。以卵蛋白致敏建立哮喘动物组模型；再给予肌注地塞米松（0．5mg/kg)治疗则为地塞米松组。利用Dot blot与Northern blot及免疫组化染色法，研究c-fos在气道上皮细胞中的表达；利用放射免疫法测定各组支气管－肺泡灌洗液（BALF）中ET－1的含量。结果：正常对照组有低水平的c-fos基因表达和ET－1合成。哮喘组豚鼠在激发30min后，气道上皮细胞c-fos mRNA表达及Fos蛋白染色阳性颗粒都达到高峰，持续2h左右。同时，BALF中ET－1的含量在30min 后也达到高峰，持续2－3h。地塞米松组的c-fos mRNA及蛋白表达水平均明显低于哮喘组（P＜0．01），但高于正常对照组；并且该组BALF中ET－1的含量也低于哮喘组（P＜0．01）。结论：c-fos基因活化与ET－1释放在哮喘豚鼠发病中都具有重要作用，两者密切相关。ET－1的释放可能受控于c-fos基因的活化。