Gestational changes in endothelin-1-induced receptors and myometrial contractions in rat.

The present experiments were performed to characterize the gestational changes in endothelin (ET)-1-induced myometrial contractions and ET receptors in rat. ET-1-induced contractions were composed of two types: increases in resting tone and rhythmic contractions. The increase in resting tone was decreased at 7 days of gestation, but increased at 20 days. The increase in amplitude and frequency of rhythmic contractions remained unchanged during days 7-14 of gestation. Continuous rhythmic contractions were not produced by ET-1 near the term. Both contractions were inhibited by the antagonists BQ 123 and Ro 46-2005 but not by RES 701-1 or BQ 788. In binding studies, total binding sites of [1251]-ET-1 were unchanged, however higher affinity binding sites appeared during pregnancy in addition to the lower affinity sites. The specific [125I]-ET-1 binding in non-pregnant and pregnant myometrium was completely inhibited by unlabelled ET-1 and Ro 46-2005. In contrast, the proportion which was inhibited by BQ 123 was decreased during pregnancy. In conclusion, characteristic gestational changes were the augmentation of ET-1-induced increased resting tone near term, and the appearance of high affinity ET-1 binding sites and an increase in BQ 123-resistant ET-1 binding sites during pregnancy. Further investigations are needed to understand the physiological role of these changes.     

Roles of endogenous nitric oxide synthase inhibitors and endothelin-1 for regulating myometrial contractions during gestation in the rat

This study investigated the roles of endogenous nitric oxide synthase (NOS) inhibitors and endothelin-1 (ET-1) for regulating myometrial contractions during gestation in the rat. Basal and stimulated cyclic GMP production with L-arginine as a NOS substrate or sodium nitroprusside (SNP) as a NO donor were significantly enhanced at the middle of gestation (14th day), while these were greatly decreased at term (22nd day), suggesting the accelerated NO production and/or up-regulation of guanylate cyclase at the middle of gestation. NOS within the myometrium was mainly Ca(2+)dependent and partly Ca(2 + )independent and remained unaffected by aminoguanidine as an inhibitor of inducible NOS in non-pregnant and gestational myometrium. NOS activity per se and endothelial NOS (eNOS) protein expression remained unchanged at the middle and term gestation. Neuronal NOS (nNOS) and inducible NOS (iNOS) proteins were undetectable. SNP at a high concentration of 100 micromol/l failed to modify the spontaneous and ET-1-induced rhythmic contractions in non-pregnant and gestational myometrium. Contents of N(G)-monomethyl-L-arginine (L-NMMA) plus asymmetric N(G),N(G)-dimethyl-L-arginine (ADMA) as endogenous NOS inhibitors and ET-1 within the myometrium were significantly decreased at 14th and 20th days of gestation, whereas these were significantly increased at term gestation (22nd day) and after delivery. There was a significant and positive correlation between endogenous NOS inhibitor content and ET-1. ET-1 within the myometrium was significantly increased with a concomitant decrease in cyclic GMP production after the intraperitoneal application of authentic L-NMMA for 2 weeks, suggesting that the impaired NO production with endogenous NOS inhibitors would result in increased ET-1 content. These results suggest that endogenous NOS inhibitors such as L-NMMA and ADMA play an important role for regulating NO production in rat myometrium. The impaired NO production due to accumulated endogenous NOS inhibitors possibly results in increased ET-1 content within the myometrium, thereby increasing myometrial contractions at term gestation and after delivery.     

阿司匹林抑制内皮素-1诱导的大鼠心脏成纤维细胞增殖

目的 探讨阿司匹林（Aspirin）对内皮素-1(ET-1)诱导的大鼠心脏成纤维细胞（CFs）增殖的干预作用及可能机制。方法 经差速贴壁法培养的新生大鼠CFs,随机分为7组：对照组、ET-1组、阿司匹林组、ET-1+ 阿司匹林1、2、5和10 mmol·L-1组。用四氮唑盐（MTT）法测定CFs数目,流式细胞仪检测CFs细胞周期,液体闪烁计数仪测定CFs 3H-脯氨酸掺入率,硝酸还原酶法测定细胞培养上清液中NO含量。结果 与对照组相比,10-7 mol·L-1 ET-1能显著促CFs增值及[3H]-Proline掺入率,降低CFs生成NO2-/NO3-的量（均P < 0.01）,1～10 mmol·L-1 阿司匹林呈浓度依赖性的缓解上述变化（均P < 0.05）; ET-1能显著提高S期细胞百分率（P < 0.01）,10 mmol·L-1 阿司匹林抑制ET-1诱导S期细胞百分率上升（P < 0.01）。结论 阿司匹林抑制ET-1诱导的CFs增殖及胶原合成可能和NO生成有关。     

Involvement of arginase in regulating myometrial contractions during gestation in the rat

This study was designed to investigate the role of arginase in regulating myometrial contractions during gestation in the rat. Arginase activity in the myometrium was significantly decreased during the 7th-21st day of gestation, with the lowest value on the 14th day. However, the enzyme activity became significantly higher at term gestation (22nd day) than that in the non-pregnant myometrium. Arginase I protein was undetectable in the non-pregnant myometrium, at 7th and 14th day of gestation and after delivery. A slight positive signal for arginase I was detectable at 21st day of gestation. However, the protein was clearly up-regulated at term gestation (22nd day), although arginase II protein was down-regulated during gestation, with the lowest value on the 14th day. Gestational changes in arginase activity negatively correlated with those in cyclic GMP production, whereas the changes positively correlated with those in endogenous nitric oxide synthase (NOS) inhibitors and endothelin-1 (ET-1) contents. Myometrial arginase activity was inhibited by N(G)-hydroxy-L-arginine as an intermediate of NO production from L-arginine in a concentration-dependent manner. Both basal and stimulated guanylyl cyclase activities were enhanced at mid- and reduced at term gestation and after delivery, thereby partly increasing cyclic GMP production at mid- and partly decreasing the nucleotide production at term gestation and after delivery. These results suggest that the decreased arginase activity at mid-gestation possibly results from the down-regulation of arginase II protein. Whereas, the enhanced overall arginase activity at term gestation seems to be because of the induced functional arginase I in concert with the attenuated arginase II expression. The enhanced arginase activity at term gestation would be implicated in increasing myometrial contractions mediated by the increased ET-1. The increased peptide production at term gestation is possibly because of the reduced cyclic GMP production resulting from enhanced arginase activity, accumulated endogenous NOS inhibitors and attenuated guanylyl cyclase activity.     

ET-1介导损伤气道上皮诱导成纤维细胞活化的信号机制

目的： 探讨p38丝裂原活化蛋白激酶(MAPK)、磷脂酰肌醇3-激酶(PI3K/Akt)在内皮素(ET)-1介导损伤气道上皮诱导上皮下成纤维细胞活化过程中的作用及对白细胞介素(IL)-6的影响。方法：将正常或经多聚左旋精氨酸(PLA)刺激的人气道上皮细胞与原代气道成纤维细胞共培养并分别加入p38 MAPK、PI3K特异性抑制剂SB203580、LY294002或ET受体A阻断剂BQ123,应用免疫组化、免疫印迹技术或ELISA检测成纤维细胞α-平滑肌肌动蛋白（α-SMA）表达、p38 MAPK、Akt的活化及成纤维细胞上清IL-6水平;制备成纤维细胞胶原凝胶并与不同方法处理的上皮细胞共培养,测量各组凝胶面积变化以了解上皮细胞对成纤维细胞收缩反应的诱导及其上述处理因素的影响。结果：与损伤上皮细胞共培养的成纤维细胞上清中ET-1、IL-6水平［（13.69±1.36） ng/L、(56.7±10.7) ng/L］明显高于与正常上皮细胞共培养的成纤维细胞上清［（3.79±0.64） ng/L、（15.5±3.2）ng/L］,BQ123、SB203580或LY294002皆不同程度减弱损伤上皮细胞诱导的IL-6释放［分别为(27.2±3.1) ng/L、(31.5±3.6) ng/L、(41.3±3.2) ng/L］;成纤维细胞与损伤气道上皮细胞共培养后p38 MAPK、Akt先后激活,BQ123减弱磷酸化p38 MAPK、Akt水平,SB203580浓度依赖性减弱Akt磷酸化水平,而LY294002对磷酸化p38 MAPK水平影响很小。与损伤气道上皮细胞共培养后成纤维细胞α-SMA表达增加,并且胶原收缩百分比明显大于与正常气道上皮共培养的成纤维细胞［(61.2±2.7)% vs (15.4±7.3)%］;BQ123、SB203580及LY294002皆不同程度减弱成纤维细胞α-SMA表达与凝胶收缩且BQ123、SB203580抑制凝胶收缩作用较LY294002更明显。结论：ET-1通过激活p38 MAPK、PI3K/Akt信号通路并促进IL-6分泌在损伤气道上皮诱导成纤维细胞活化过程中发挥关键作用。     

The anti-inflammatory mechanism of heme oxygenase-1 induced by hemin in primary rat alveolar macrophages

Alveolar macrophages (AMs) can initiate lung inflammation by producing pro-inflammatory cytokines and chemokines, but they participate actively in the prevention of inflammation during acute lung injury (ALI). Heme oxygenase-1 (HO-1) is mainly expressed in AMs and has anti-inflammatory properties in ALI, but the anti-inflammatory mechanisms of HO-1 are largely unknown. In this study, AMs were treated with saline, LPS (1 μg/ml), hemin (10 μM), zinc protoporphyrin (ZnPP; 10 μM, 1 h prior to LPS and hemin), SB203580 (10 μM, 1 h prior to LPS and hemin), or their combination up to 24 h. The specific HO-1 inhibitor ZnPP and SB203580 were used to inhibit the effects of HO-1 and the phosphorylated p38 mitogen-activated protein kinase (MAPK), respectively. The protein levels of HO-1 and p38 MAPK were analyzed by western blotting; arginase activity was measured in lysates obtained from cultured cells; nitric oxide production in the extracellular medium of AMs cultured for 24 h was monitored by assessing nitrite levels; the phagocytic ability of macrophage was measured by neutral red uptake. IL-10 of culture supernatants in AMs was determined by enzyme-linked immunosorbent assay. The results indicated that HO-1 induced by hemin increased arginase activity and phagocytic ability and decreased iNOS activity via p38 MAPK pathway in primary rat AMs. These changes and p38 MAPK may be the anti-inflammatory mechanism of HO-1 induced by hemin in primary rat AMs.     

内皮素性大鼠门静脉高压模型的建立

目的： 建立内皮素-1(ET-1)引起门静脉压力升高的动物模型。方法: 正常雄性SD大鼠48只，随机分为生理盐水组、ET-1低剂量组(0.3 μg/kg)，ET-1中剂量组(1.0 μg/kg)和ET-1高剂量组(3.0 μg/kg)。生理盐水组大鼠经股静脉注入生理盐水，其余各组大鼠按相应剂量经股静脉注入ET-1溶液，观察门静脉压力和颈动脉压力的变化情况,并筛选出能使门静脉压力升高最适宜的剂量；另取15只大鼠随机分为对照组、ETAR阻断剂(BQ-123)组和ETBR阻断剂(BQ-788)组，实验开始前30 min经各组大鼠股静脉分别注入生理盐水、ETR阻断剂BQ-123(给药剂量为12.5 μg/kg)和BQ-788(给药剂量为15 μg/kg)，然后以选定的适宜剂量匀速注入ET-1溶液，观察各组大鼠门静脉压力变化。结果: 不同剂量的ET-1均能使门静脉压力升高，尤以高剂量组最为明显；而提前注入ETR阻断剂之后，再注入ET-1溶液门静脉压力虽然升高，但升高的幅度较小。结论: 成功创建了内皮素性大鼠门静脉高压模型，此模型可用于研究ET-1在PHT发病机制中的作用和药物对PHT时血中ET-1的影响。     

Nitric oxide prevents rat duodenal contractions induced by potentially noxious agents

After abdominal surgery, luminal HCl fails to induce duodenal contractions in anaesthetized rats. Elevated tissue levels of nitric oxide (NO) and prostaglandins possibly contribute to this observation. The aim of this study was to compare the effects of luminal capsaicin (1.2 mg mL-1), ethanol (15%) and high partial pressure of CO2 (>250 mmHg) with those of HCl (10 mM) in anaesthetized rats. Motility (intraluminal pressure), mucosal permeability [blood-to-lumen clearance of 51Cr-EDTA (51Chromium-labelled ethylenediaminetetraacetate)] and duodenal mucosal bicarbonate secretion (DMBS) were recorded. Three groups of animals were studied: (1) controls, (2) pretreatment with the NO synthase inhibitor N-nitro-L-arginine-methyl-ester (L-NAME) and (3) pretreatment with the cyclo-oxygenase inhibitor indomethacin. Neither capsaicin, ethanol, CO2 nor HCl induced duodenal contractions or affected DMBS in control rats. However, L-NAME induced duodenal contractions that were augmented by capsaicin, ethanol and HCl, but not by CO2. Indomethacin also induced contractions that were reversibly diminished by capsaicin and HCl, but not by ethanol or CO2. Significant increases in mucosal permeability occurred during ethanol perfusion in indomethacin- and L-NAME pretreated rats. In conclusion, NO probably plays a key role in preventing duodenal contractions in response to luminally HCl, capsaicin and ethanol. The HCl-induced effect on motility appears to be independent of CO2 and is not caused by alteration in mucosal integrity.     

Involvement of local ischemia in endothelin-1 induced lesions of the neostriatum of the anaesthetized rat

Summary The present study examines the possibility that lesions induced by intrastriatal injections of endothelin-1 (ET-1, 0.43 nmol/0.5 µl) are ischemic in nature due to a vasoconstriction of the cerebral microvessels. In time course and dose-response experiments with ET-1 and in comparisons with ET-3, the volume of the lesions has been determined based mainly on the disappearance of striatal nerve cells, using a computer assisted morphometrical analysis. The blood flow in the neostriatum close to the site of injection of ET-1 was determined acutely by Laser-Doppler flowmetry. The acute metabolic effects of ET-1 were also studied on striatal superfusate levels of lactate, pyruvate, dopamine and its metabolites DOPAC (3,4-dihydroxyphenylacetic acid) and homovanilic acid (HVA) using an instrastriatal microdialysis probe. Dose related striatal lesions were observed with ET-1 (0.043–0.43 nmol) with a peak lesion volume after 24–48 h and the possible existence of a penumbra area. ET-3 showed a reduced potency to produce striatal lesions compared to ET-1. The lesions induced by ET-1 were prevented by coinjection with dihydralazine, a vasodilator drug. Acutely ET-1 (0.43 nmol/0.5 µl) produced a prolonged reduction of the cerebral blood flow down to 40% of control values and temporary increases of striatal lactate and DA efflux, the latter change being very marked. Also a significant reduction of DOPAC and HVA was observed. These neurochemical changes were all prevented by treatment with dihydralazine. These results indicate that ET-1 injected in the neostriatum may produce lesions by causing local ischemia, related to its vasoconstrictor activity and possibly also to an activation of ET-1 receptors in the astroglial-endothelial complex. Based on the present results it seems possible that ET-1 may participate in the multifactorial pathogenesis of cerebral ischemia.     

Role of transient receptor potential ankyrin subfamily member 1 in pruritus induced by endothelin-1

Noxious cold reduces pruritus and transient receptor potential ankyrin subfamily member 1 (TRPA1), a non-selective cation channel, is known as a noxious cold-activated ion channel. Recent findings implicated the involvement of TRPA1 in pain induced by endothelin-1 (ET-1). Therefore, we evaluated its potential role in pruritus induced by ET-1. We found that ruthenium red (RR; a nonselective TRP inhibitor) and AP18 (a TRPA1 antagonist) significantly increased scratching bouts caused by ET-1, while capsazepine (a TRPV1 antagonist) and morphine showed no effects in the ET-1-induced scratching response. However, RR and capsazepine significantly reduced scratching bouts caused by histamine. Our results suggested that activation of TRPA1 could suppress itch induced by ET-1 and this is not related to pain induced by ET-1.     

Post-injury stretch promotes recovery in a rat model of muscle damage induced by lengthening contractions

We investigated the cellular mechanisms and therapeutic effect of post-injury stretch on the recovery process from muscle injury induced by lengthening contractions (LC). One day after LC, a single 15-min bout of muscle stretch was applied at an intensity of 3 mNm. The maximal isometric torque was measured before and at 2–21 days after LC. The myofiber size was analyzed at 21 days after LC. Developmental myosin heavy chain-immunoreactive (dMHC-ir) cells, a marker of regenerating myofibers, were observed in the early recovery stage (2–5 days after LC). We observed that LC-induced injury markedly decreased isometric torque and myofiber size, which recovered faster in rats that underwent stretch than in rats that did not. Regenerating myofiber with dMHC-ir cells was observed earlier in rats that underwent stretch. These results indicate that post-injury stretch may facilitate the regeneration and early formation of new myofibers, thereby promoting structural and functional recovery from LC-induced muscle injury.     

胰岛素对糖尿病大鼠内皮素缩血管作用的影响

目的:研究高糖血症时胰岛素对内皮素-1(ET-1)缩血管作用的影响。方法:复制高糖血症大鼠模型;将高糖大鼠和正常大鼠的离体主动脉血管环置于无胰岛素和高于生理浓度(40mIU/L)胰岛素的KH液中,观察两组大鼠血管对10^-9mol/LET-1的反应。结果:高糖大鼠血管对ET-1的反应明显弱于正常大鼠(P<0.01);高浓度胰岛素可减弱ET-1对正常大鼠血管的收缩作用(P<0.01);胰岛素不能减弱ET-1对高糖大鼠血管的收缩作用。结论:(1)长期高糖血症使血管对ET-1的反应降低;(2)胰岛素可减弱ET-1对正常大鼠血管的收缩作用;(3)长期高糖血症使胰岛素对ET-1缩血管活性的影响减小。     

Evidence for a preventive action of the vigilance-promoting drug modafinil against striatal ischemic injury induced by endothelin-1 in the rat

We have studied the ability of the vigilance-promoting drug modafinil to counteract the ischemic lesion produced by a unilateral microinjection of endothelin-1 (ET-1) in the neostriatum of the rat using a combined morphometrical, biochemical, cardiovascular and behavioral analysis. ET-1 was injected unilaterally into the neostriatum. The ET-1-induced lesion volume, which was determined by a computer-assisted morphometrical analysis, was reduced by the 7-day modafinil treatment (10, 30, and 100 mg/kg i.p.) in a dose-related way. Modafinil also produced a dose-related counteraction of the ET-1-induced increase of perfusate lactate levels, as determined by intrastriatal microdialysis without affec ting the ET-1 induced reduction of striatal blood flow, as determined by laser-Doppler flowmetry. The ipsilateral rotational behavior induced by apomorphine in the ET-1-lesioned rats was reduced dose-dependently by modafinil treatment. Thus, morphological, neurochemical, and behavioral evidence that the putative ischemic striatal injury induced by microinjection of ET-1 in the rat neostriatum is counteracted in a dose-dependent way by modafinil treatment has been obtained. The mechanism does not appear to involve an increase in striatal blood flow. It is instead speculated that its powerful preventive action in striatal ischemic injury may be related to a reduced anaerobic metabolism.     

Force-independent expression of c-fos mRNA by endothelin-1 in rat intact small mesenteric arteries

AIM: Wall stress-independent signalling pathways were studied for endothelin-1 (ET-1)-induced c-fos expression in rat intact mesenteric small arteries. METHODS: Arteries were kept unmounted in Krebs buffer, equilibrated for 1 h and stimulated with vasoactive substances for 15-60 min. The c-fos mRNA expression was determined by real-time polymerase chain reaction. RESULTS: Stimulation with fetal bovine serum (FBS), phorbol 12-myristate 13-acetate (PMA) and ET-1 caused about a doubling of c-fos mRNA. The ET-1-induced c-fos expression was steady (15-60 min) and was inhibited by the inhibitor of the ET(A) receptor, BQ-123. Platelet-derived growth factor-B, angiotensin II and U46619 did not cause increased c-fos mRNA levels. The broad specificity inhibitor staurosporine inhibited the response to ET-1, but inhibitors of Rho-A kinase and phosphatidylinositol 3-kinase had no effect. However, inhibitors to tyrosine kinases, the MAP kinases [extracellular signal-regulated kinase 1/2 (ERK1/2), c-Jun amino-terminal kinase, p38], and to conventional protein kinase C showed no inhibition. Consistent with these findings, ET-1 did not cause activation of ERK1/2, a finding also seen in vessels held under pressure. In contrast, ET-1-induced c-fos expression was inhibited by the calcium chelator BAPTA, suggesting a role for intracellular calcium. This possibility was supported by the finding that raising the extracellular K(+) concentration caused increased expression of c-fos in a concentration-dependent manner. CONCLUSION: The results suggest that in the absence of wall stress, ET-1 is able to induce increased expression of c-fos independent of traditional growth pathways, such as MAP kinase. The mechanism appears to be calcium-dependent.     

应激对大鼠心肌细胞线粒体膜通透性转换孔开放的影响及其分子基础的研究 

目的: 观察应激对大鼠心肌线粒体膜通透性转换孔(PTP)开放的影响,探讨PTP开放的分子基础。方法: 建立应激动物模型,分别束缚不同时间后处死所有大鼠,分光光度法检测线粒体PTP开放程度、Western blot方法检测线粒体Bcl-2\, Bax蛋白表达水平。结果:应激可导致大鼠心肌线粒体膜PTP开放,Bcl-2表达水平降低、Bax水平增高。 结论: PTP开放为应激性心肌损伤的重要线粒体机制;Bcl-2表达降低\, Bax水平上调则为PTP开放的重要分子基础。     

ERKs及细胞内游离钙在内皮素-1诱导心肌细胞肥大反应中的作用

目的:研究细胞外信号调节激酶(ERKs)及细胞内游离钙(i)在内皮素-1(ET-1)介导心肌细胞肥大反应中的作用及机制。方法:利用培养的新生大鼠心肌细胞,①以蛋白合成速率、蛋白含量及细胞表面积为心肌肥大反应的指标;②用滤纸法测定ERKs活性;③用Fura-2/AM作为钙荧光指示剂测定心肌[Ca²⁺]i浓度。结果:①ET-1浓度依赖性增加新生大鼠心肌细胞蛋白质含量和心肌细胞表面积、ERKs活性及[Ca²⁺]i浓度,以上作用可被ET_A受体拮抗剂BQ123所完全抑制,被百日咳毒素(PTX)部分抑制,而ET_B受体拮抗剂BQ788则无效;②ERKs激酶特异性抑制剂PD98059可完全抑制ET-1激活ERKs的作用,钙通道拮抗剂硝苯地平可明显抑制ET-1介导的[Ca²⁺]i浓度增加,但二者皆仅部分抑制ET-1介导的心肌细胞肥大反应;③蛋白激酶C(PKC)选择性抑制剂staurosporine并不能明显抑制ET-1介导的ERKs激活,但可抑制ET-1介导的的[Ca²⁺]i浓度增加及心肌细胞肥大反应。结论:ET-1主要通过ET_A受体并经PTX敏感的G-蛋白介导心肌细胞肥大反应,该作用至少涉及两条途径:①通过PKC介导的心肌[Ca²⁺]i浓度增加;②不通过PKC介导的ERKs激活。     

Tetrodotoxin-resistant contractions induced by electrical stimulation of bladder muscle from man, rabbit and rat

Isolated detrusor preparations from man, rabbit and rat were suspended in an organ bath and isometric tension was recorded. The preparations were stimulated electrically in the presence of Bay K8644 and nifedipine before and after neuronal blockade with tetrodotoxin. Transmural electrical stimulation produced frequency-dependent contractions in all preparations. Bay K8644 significantly increased and nifedipine decreased these contractions. TTX effectively suppressed the response to electrical field stimulation in all species. When Bay K8644 was added to TTX blocked preparations, the responses to electrical stimulation were partly restored in bladder strips from man and rat. No increase in response was seen in the rabbit preparations. However, if the extracellular K+-concentration was increased to 10 mM (which per se did not affect the response) Bay K8644 significantly increased the contractions. All responses elicited by electrical stimulation in the presence of TTX were abolished by nifedipine. It is concluded that if the bladder smooth muscle is exposed to factors that can increase its sensitivity to contractile agents, this may result in uncontrolled (unstable) bladder contractions. Such contractions may use the 'normal' transmitter substances, but may be triggered at a lower stimulus intensity than normal. As a non-specific increase in membrane excitability seems to be associated with an influx of calcium through voltage-sensitive calcium channels, calcium antagonists, together with agents specifically blocking relevant transmitter substances, would offer an effective therapy against the unstable bladder.     

Vasocontractions of the in-vitro toad aortas induced by endothelin-1 and sarafotoxin-S6b

Dose-dependent tension curves were recorded from the in vitro toad aortas by administration of endothelin-1 and sarafotoxin-S6b. The maximal contractile tensions by both drugs were evoked at a 10^?8 M concentration. By a single dose application (10^?8 M) of endothelin-1 and sarafotoxin-S6b to both endothelium-preserved and denuded vessels, the induction of the endothelium-dependent vasocontraction occurs after 2 min of administration. Ultrastructural changes of Weibel-Palade bodies such as decrease in electron density, swelling with a wide peripheral halo, and expulsion of their contents in a manner of exocytosis become evident within 2 min after administration of these drugs. These findings indicate that some vasocontractile substances in Weibel-Palade bodies are extracellularly discharged by endothelin-1 and sarafotoxin-S6b. © 1993 Wiley-Liss, Inc.