Endothelin-1 inhibitsl-type Ca currents enhanced by isoproterenol in guinea-pig ventricular myocytes

To investigate the action of Endothelin-1 (ET-1) on L-type Ca currents (I _Ca,L) in guinea-pig ventricular cells, whole-cell currents were recorded at 36-37° C in enzymatically isolated myocytes. ET-1 ( 10 nM) suppressed the basal I_ca,L to 79 ± 8% of control at 20 nM. Bath application of isoproterenol (ISO; 10 nM) enhanced I_Ca,L to 192±28% with about a – 10-mV shift of its relationship with membrane potential. ET-1 concentration dependently inhibited this ISO-enhanced I_Ca,L with a half-maximally inhibitory concentration (IC₅₀) of 168 pM. The inhibitory actions of ET-1 were antagonised by BQ-123 (300 nM), cyclo(d-Asp-l-Pro-d-Val-l-Leu-d-Trp), a specific ETA receptor antagonist. Histamine-enhancedI _Ca,L was also suppressed by ET-1, butI _Ca,L potentiated by internal adenosine 3,5-cyclic monophosphate (cAMP) was unaffected. Preincubation of myocytes with pertussis toxin (PTX, at 5 g/ml for >60 min at 36° C) completely occluded the ET-1 action. Thus, stimulation of ET_A receptors by subnanomolar ET-1 inhibitsI _Ca,L via PTX-sensitive G-proteins.     

Different endothelin receptor subtypes are involved in phospholipid signalling in the proximal tubule of rat kidney

 Phospholipid signalling mediated by endothelin (ET) receptor subtypes was studied in the rat proximal tubule. In freshly isolated proximal tubule cells, ET-1, ET-2 and sarafotoxin S6c (S6c) evoked an increase in 1,2-diacylglycerol (DAG), inositol 1,4,5-trisphosphate (InsP ₃) and phosphocholine (PCho), suggesting stimulation of both phosphatidyl-inositol 4,5-bisphosphate- and phosphatidyl-choline-specific phospholipase C (PLC), while ET-3 increased only DAG and PCho, presumably via phosphatidyl-choline-dependent PLC. Renal cortical slices were also stimulated by the above-mentioned agonists, followed by isolation of either brush border (BBM) or basolateral (BLM) membranes for which mass measurements of inositol lipids and DAG were performed. In BBM, DAG increased in response to ET-1, ET-2 and ET-3, and was followed by protein kinase C (PKC) translocation to the BBM, while in BLM, DAG formation and translocation of PKC were observed only in response to ET-3, suggesting spatial segregation of signalling systems between two membane domains of proximal tubule cells. Tyrphostine, pertussis toxin (PTX) or cholera toxin (CTX) did not influence ET-mediated signalling in either of the membranes, suggesting involvement of PTX- and CTX-insensitive G-protein-mediated stimulation of PLCβ by ET receptors. ET-dependent stimulation of PLC in BBM and BLM was used as a tool to examine the presence of different ET receptor subtypes in these two cell membrane domains. BQ123, an inhibitor of ET_A receptors, did not prevent ET-1-mediated signalling in BBM, but an ET_A,B antagonist, bosentan, inhibited ET-3-mediated signalling in BBM. In addition, an ET_B agonist, S6c, stimulated PLC in BBM. Neither BQ123 nor bosentan inhibited ET-3 signalling in BLM. Therefore, these data strongly suggest the presence of ET_B receptors coupled to phosphatidyl-inositol 4,5-bisphosphate- and phosphatidyl-choline-dependent PLC in BBM and ET_C receptors linked to phosphatidyl-choline-dependent PLC in BLM. Received: 21 November 1995 / Received after revision and accepted: 5 February 1996     

Immunohistochemical localization of endothelin-like immunoreactivity in human tooth germ and mature dental pulp

Summary The distribution in oral tissues of endothelin, a multifunctional peptide originally identified within endothelial cells, and subsequently in some epithelial cells, neurons and neuroendocrine cells, has not been investigated yet. We have studied the localization of endothelin-like immunoreactivity in human tooth germ and mature dental pulp by immunohistochemical techniques. Such immunoreactivity was detected only within endothelial cells in both mature dental pulp and developing tooth. Arteries and veins of various sizes as well as small thin vessels displayed endothelin-like immunoreactivity. In the tooth germ, the cells of the enamel organ or the precursors of the odontoblasts were found unreactive. In the mature pulp, no cells of the stroma or nerves displayed endothelin-like immunoreactivity. These findings suggest that vascular endothelium may be the only source of endothelin in human dental tissues. It is tentatively proposed that endothelin released in mature tooth pulp may participate in the regulation of the pulpal blood flow. Although the possible role of endothelin in developing tissues is far from being clear, the mitogenic effects and the proto-oncogenes expression induced by endothelin in some cells raise the possibility that this peptide might also play a role during tooth development.     

犬腹部5.56mm弹致伤后早期肝脏的变化及其机理

本研究观察了犬腹部高速投射物伤后早期肝功能的变化及内皮素、压力波在其中的作用。结果发现：伤后肝组织ＭＤＡ含量明显增高（Ｐ〈０．０１），ＡＴＰ水平显著下降；而肝血流量于伤后一直低于伤前；血清内皮素含量在伤后明显升高，其变化与肝血流量下降间有显著负相关关系。肝脏损伤的发生与肝血流减少及压力波的直接作用有关，而肝血流减少的原因则可能与失血性应激所致的血流再分配及内皮素的作用有关。     

抑郁症患者血浆内皮素水平的研究

目的探讨抑郁症患者血浆内皮素（ＥＴ）水平及其与下丘脑垂体肾上腺（ＨＰＡ）轴之间可能的联系。方法采用放射免疫法测定４２例抑郁症患者及３０名正常对照的晨８时血浆ＥＴ１及皮质醇浓度。结果单、双相抑郁血浆ＥＴ１与皮质醇浓度均显著高于正常对照（Ｐ＜００１）,但仅双相抑郁血浆ＥＴ１与皮质醇有直线相关关系（ｒ＝０５３,Ｐ＜００１）。结论抑郁症患者血浆ＥＴ１水平升高可能与部分（双相）抑郁患者ＨＰＡ轴功能亢进有关。     

Up-regulation of endothelin (ETA and ETB) receptors and down-regulation of nitric oxide synthase in the detrusor of a rabbit model of partial bladder outlet obstruction

Bladder outlet obstruction (BOO) is associated with altered bladder structure and function. Endothelin-1 (ET-1) has mitogenic and potent contractile properties. There are two ET receptors: ET_A and ET_B. Nitric oxide synthase (NOS) is the enzyme responsible for the synthesis of nitric oxide (NO) which is involved in smooth muscle relaxation. We investigated whether there are any changes in the density of ET-receptors and NOS in the detrusor and bladder neck in a rabbit model of BOO. Partial BOO was induced in adult male New Zealand White rabbits. Sham operated age-matched rabbits acted as controls. After six weeks the urinary bladders were excised and detrusor and bladder neck sections incubated with radioligands for ET-1, ET_A and ET_B receptors and with [³H]–l-NOARG (a ligand for NOS). NADPH histochemistry was also performed. BOO bladder weights were significantly increased (P=0.002). ET-1 binding and ET_A receptor binding sites were significantly increased in the BOO detrusor smooth muscle (P=0.04, P=0.03 respectively) and urothelium (P=0.002, P=0.02 respectively). ET_B receptor binding sites were also significantly increased in the BOO detrusor smooth muscle (P=0.04). However, there was no change in the BOO bladder neck. NOS was significantly decreased in the detrusor smooth muscle (P=0.003) and urothelium (P=0.0002). In the bladder neck NOS was also significantly reduced in the urothelium (P=0.003). NADPH staining was decreased in the detrusor and bladder neck. The up-regulation of ET receptors along with the down-regulation of NOS in the detrusor may contribute to the symptoms associated with BOO. Since ET-1 has a mitogenic role, especially via its ET_A receptors, the increase in ET_A receptors may also be involved in detrusor hyperplasia and hypertrophy in BOO. ET antagonists may therefore have a role in the treatment of patients with BOO. Received: 24 March 1999 / Accepted: 25 June 1999     

拮抗内皮素促进深Ⅱ度烫伤创面愈合的实验研究

观察内皮素受体桔抗剂PD142893对深Ⅱ度烫伤创面愈合的作用。SD大鼠随机分成PD142893组、生理盐水两组,测定烫伤前后创面含水量、丙二醛(MDA)产量和超氧歧化酶(SOD)活性。伤后PD142893组含水量明显低于生理盐水组:PD142893组MDA量上升后快速下降,生理盐水组却呈直线上升;PD142893组SOD活性下降程度低,回升快。PD142893组较生理盐水组创面愈合时间短、质量高。提示烫伤早期给予PD142893拮抗ET,可减轻创面渗出及脂质过氧化损害.使大鼠深Ⅱ度烫伤愈合良好。     

不同分期高血压病血浆内皮素变化

目的 为了解内皮素（ＥＴ）是否与高血压病（ＥＨ）及其靶器官受损有联系。方法 分析了５４例不同分期ＥＨ和２７例对照血浆ＥＴ。结果 ＥＨ组血浆ＥＴ水平较对照组增高,差异显著（Ｐ〈０．０１）。而在ＥＨ各分期组中,Ⅰ期（２８例）与对照组血浆ＥＴ水平相近,差异不显著（Ｐ〉０．０５）;Ⅱ期（１１例）和Ⅲ期（１５例）分别较对照组和Ⅰ期患者明显增高,差异非常显著（Ｐ〈０．０１）。１５例超声心动图诊断左室肥厚者和１     

急性肾小球肾炎患儿血浆内皮素,降钙素相关基因肽和心钠素的变化及意义

目的了解急性肾小球肾炎患儿血浆内皮素、降钙素相关基因肽和心钠素的变化。方法应用放射免疫法测定血浆内皮素、降钙素相关基因肽和心钠素的水平。结果患儿血浆内皮素水平（15．4±70．1ng／L）明显高于正常儿童（42.0±14.4ng／L）,P＜0.0001;患儿血浆降钙素相关基因肽水平（86．0±41．8ng／L）与正常儿童（65．3±48．5ng／L）无显著性差异,P＝0．05;患儿血浆心钠素水平（77．2±34.8nmol／L）明显低于正常儿童（166．2±31．2nmol／L）,P＜0．0001。结论应用外源性降钙素相关基因肽、心钠素对儿童急性肾小球肾炎的临床治疗可能具有重要的意义。     

脑出血患者血浆内皮素和自由基检测的临床意义及相关性研究

目的:探讨血浆内皮素(ET)和血清酯质过氧化物(LPO)在脑出血病理过程中的作用及相互关系。方法:测定了60例脑出血急性期和亚急性期血浆ET和血清LPO的水平,并分别与单纯高血压患者及正常人各30例作对照进行分析。结果:脑出血急性期血浆ET及血清LPO水平升高(P<0.01),其升高水平与神经缺损程度、出血量呈正相关,血浆ET含量与血清LPO呈直线相关关系。结论:ET与LPO在脑出血病理过程中具有一定作用,加重出血后脑组织损伤。