Cytosolic-free calcium transients in cultured vascular smooth muscle cells: microfluorometric measurements

Microfluorometric recordings were made of changes in the concentration of cytosolic-free calcium in cultured rat vascular smooth muscle cells treated with quin 2, an intracellularly trapped dye, under several conditions. Nitroglycerin decreased calcium in both the presence and absence of extracellular calcium and strongly and progressively decreased the extent of transient increases in calcium induced by repeated applications of caffeine in the absence of extracellular calcium. Therefore nitroglycerin probably decreases cytosolic-free calcium by accelerating the extrusion of calcium through the sarcolemmal membrane.     

Regional changes in calcium underlying contraction of single smooth muscle cells

The role of calcium in regulating the contractile state of smooth muscle has been investigated by measuring calcium and contraction in single smooth muscle cells with the calcium-sensitive dye fura-2 and the digital imaging microscope. The concentration of free calcium in the cytoplasm increased after stimulation of the cells by depolarization with high potassium or by application of carbachol. Changes in calcium always preceded contraction. The increase in calcium induced by these stimuli was limited to less than 1 microM. Calcium within the nucleus was also subject to a limitation of its rise during contraction. Intranuclear calcium rose from 200 nM at rest to no more than 300 nM while cytoplasmic calcium rose to over 700 nM. These apparent ceilings for both cytoplasmic and intranuclear calcium may result either from negative feedback of calcium on cytoplasmic and nuclear calcium channel gating mechanisms, respectively, or from the presence of calcium pumps that are strongly activated at the calcium ceilings.     

Relaxation of isolated gastric smooth muscle cells by vasoactive intestinal peptide

Vasoactive intestinal peptide caused a prompt, dose-dependent relaxation of isolated gastric smooth muscle cells of the guinea pig and a significant increase in intracellular adenosine 3',5'-monophosphate coincidentally with optimum relaxation. Relaxation was augmented by a threshold concentration of isobutyl methylxanthine. The direct relaxant effect of vasoactive intestinal peptide and the distribution of nerves containing this peptide to circular smooth muscle support the view that vasoactive intestinal peptide is the neuromuscular transmitter of enteric inhibitory nerves.     

Free calcium at rest during "catch" in single smooth muscle cells

Tension and intracellular free calcium concentration [( Ca2+]i) were measured simultaneously in single smooth muscle cells isolated from the anterior byssus retractor muscle (ABRM) of Mytilus edulis that were loaded with the fluorescent Ca2+ indicator fura-2. Electrical stimulation evoked a transient elevation of [Ca2+]i associated with a "catch" contraction. During the catch state, however, [Ca2+]i was effectively at its resting level and was unaffected by 5-hydroxytryptamine, which induced a rapid relaxation from catch. The results indicate that a maintained high [Ca2+]i is not required for the maintenance of catch tension in intact ABRM and that there was no significant change in [Ca2+]i upon abolition of catch.     

Platelet-mediated cholesterol accumulation in cultured aortic smooth muscle cells

Cholesterol accumulates within smooth muscle cells and macrophages in atherosclerotic lesions, thereby contributing to the progressive enlargement of these lesions. The mechanism of this cellular accumulation of cholesterol is not known. The possibility that platelets may have a role in the cellular cholesterol accumulation that occurs during atherogenesis was investigated. Incubation of thrombin-activated washed rat platelets (or platelet-free supernatants prepared from thrombin-activated platelets) with cultured rat aortic smooth muscle cells induced cholesteryl ester lipid droplet accumulation within the smooth muscle cells. No cholesteryl ester lipid droplets accumulated when smooth muscle cells were incubated with unactivated platelets. Smooth muscle cell lipid droplet accumulation occurred in the absence of serum lipoproteins and was not inhibited by mevinolin, a drug that blocks cholesterol synthesis. These findings suggest that activated platelets may release cholesterol, which can be accumulated by cells and stored as lipid droplets.     

Regulation of calcium concentration in voltage-clamped smooth muscle cells

The regulation of intracellular calcium concentration in single smooth muscle cells was investigated by simultaneously monitoring electrical events at the surface membrane and calcium concentration in the cytosol. Cytosolic calcium concentration rose rapidly during an action potential or during a voltage-clamp pulse that elicited calcium current; a train of voltage-clamp pulses caused further increases in the calcium concentration up to a limit of approximately 1 microM. The decline of the calcium concentration back to resting levels occurred at rates that varied with the calcium concentration in an apparently saturable manner. Moreover, the rate of decline at any given calcium concentration was enhanced after a higher, more prolonged increase of calcium. The process responsible for this enhancement persisted for many seconds after the calcium concentration returned to resting levels. Thus, the magnitude and duration of a calcium transient appear to regulate the subsequent calcium removal.     

Antagonistic adrenergic-muscarinic regulation of M current in smooth muscle cells

The beta-adrenergic agonist isoproterenol and analogs of adenosine 3',5'-monophosphate (cAMP) induced a potassium current, M current, in freshly dissociated gastric smooth muscle cells. Muscarinic agonists suppress this current, apparently by acting at a locus downstream from regulation of cAMP levels by adenylate cyclase and phosphodiesterase. Thus, M current can be induced by an agent and regulated in antagonistic fashion by beta-adrenergic and muscarinic systems.     

家兔子宫内膜细胞和平滑肌细胞的分离培养及鉴定

为了建立一种高效的子宫细胞分离培养方法,用酶消化、过滤、离心与差速贴壁纯化相结合的方法分离培养家兔子宫细胞,分别以上皮细胞角蛋白、波形蛋白、α-平滑肌肌动蛋白等为抗原的免疫荧光对分离培养的细胞进行鉴定,并采用流式细胞仪分析细胞纯度。结果表明,家兔子宫内膜上皮细胞培养24 h后大部分贴壁,培养3 d左右形成单层细胞集落,呈角蛋白阳性,细胞圆形或椭圆形,胞质呈红色,核呈蓝色,纯度达96%以上;子宫内膜基质细胞培养0.5 h后即有贴壁,培养2 d后呈单层细胞集落状生长,呈波形蛋白阳性,细胞多边形或梭形,胞质呈红色,核呈蓝色,纯度达95%以上;平滑肌细胞培养24 h后大部分贴壁,6~7 d融合成片,呈α-平滑肌肌动蛋白阳性,细胞大都长梭形,胞质呈红色,核呈蓝色,纯度达98%以上。说明该方法能够成功分离并得到高产量、高纯度、高增殖能力的子宫内膜细胞及平滑肌细胞。     

In vitro studies of single isolated beating heart cells

Rat heart cells, separated by trypsin treatment and grown attached to glass in a liquid medium, exhibit periodic contractions similar to a whole beating heart. The rate of beating, which is up to 150 beats per minute, is affected by cardiac drugs and by metabolic substrates and inhibitors.     

五味子木脂素舒张大鼠离体气管平滑肌的功能研究

【目的】探讨五味子木脂素6种单体成分对大鼠离体气管平滑肌张力的影响及其舒张气管平滑肌的作用机制。【方法】采用离体气管灌流法,观测终浓度为10^-7~10^-3 mol/L的五味子醇甲、五味子醇乙、五味子甲素、五味子乙素、五味子丙素、五味子酯甲和体积分数1‰二甲基亚砜（DMSO,对照）对静息状态及乙酰胆碱（ACh）预收缩状态下大鼠离体气管环张力的影响。用L型Ca²⁺通道阻滞剂维拉帕米（10^-5 mol/L）、β-肾上腺素受体阻断剂普萘洛尔（10^-5 mol/L）和体积分数1‰ DMSO（对照）预孵育大鼠离体气管环15 min,然后依次加入浓度为10^-5~10^-3 mol/L 的五味子醇甲,观测维拉帕米和普萘洛尔对五味子醇甲舒张气管作用的影响。【结果】与对照比较,不同浓度的6种五味子木脂素单体对静息状态下的气管环张力均无显著影响（P>0.05）。五味子醇甲、五味子醇乙、五味子甲素和五味子乙素对ACh预收缩的气管环张力相较对照具有显著抑制作用,且呈剂量依赖性（P<0.001）,最大抑制率分别为（92.12±3.28）%,（78.23±10.20）%,（62.95±12.93）%及（46.58±4.92）%;而五味子酯甲和五味子丙素对ACh 预收缩气管环张力无明显影响（P>0.05）。与DMSO对照组相比,五味子醇甲对大鼠离体气管环的舒张作用可被维拉帕米明显减弱（P<0.001）,最大抑制率降低了（26.24±8.42）%,但普萘洛尔对其作用无显著影响（P>0.05）。【结论】五味子醇甲、五味子醇乙、五味子甲素和五味子乙素可呈剂量依赖性地舒张大鼠离体气管平滑肌,其中五味子醇甲的作用机制可能与阻断L型Ca²⁺通道有关。     

Cytosolic calcium during contraction of isolated mammalian gastric muscle cells

During activation of visceral smooth muscle there is an increase in cytosolic-free calcium, but the source (intracellular calcium release or calcium influx), kinetics, and stoichiometry of this increase have not been determined. Here, the fluorescent indicator, quin2-acetoxymethyl ester, was used to measure directly cytosolic-free calcium during contraction of isolated stomach muscle cells induced by the two neuropeptides cholecystokinin-octapeptide and Met-enkephalin as well as acetylcholine. An increase in cytosolic-free calcium was seen that was (i) dependent on the concentration of contractile agonist, (ii) derived from intracellular sources (that is, not significantly affected by removal of ambient calcium or addition of a calcium channel blocker), and (iii) kinetically and stoichiometrically related to net calcium efflux and contraction. In contrast, the increase in cytosolic-free calcium induced by depolarizing concentrations of potassium was caused by influx of calcium through voltage-dependent calcium channels.     

鸡胚肺动脉内皮细胞与平滑肌细胞的分离培养及鉴定

探索简单快速实用的鸡胚肺动脉内皮细胞和平滑肌细胞培养方法:在严格无菌条件下对肺动脉内皮细胞和平滑肌细胞分离培养,待细胞融合度达约80%时进行传代,得到的内皮细胞利用差速消化法纯化,并观察2种细胞形态特征及培养特性,待细胞稳定生长后,采用荧光免疫组化技术鉴定细胞,并进行冻存和复苏,观察复苏后细胞活性。结果显示:24 h后组织块周围即有少量细胞爬出,内皮细胞大量生长后呈突起状排列,立体感强,平滑肌细胞在培养后的第5天呈现"峰谷"样外观,经免疫荧光法证明是内皮细胞和平滑肌细胞的纯培养,冻存于液氮中1~2个月复苏后细胞的活性都较好,可以恢复旺盛生长。结论:本研究提出的组织贴块法能成功获得内皮细胞和平滑肌细胞的纯培养,比酶消化法操作简单,更适合小血管内皮细胞、平滑肌细胞的原代培养。     

血根碱对大鼠肠平滑肌细胞收缩的抑制作用

采用酶消化法原代培养大鼠肠平滑肌细胞,用倒置相差显微镜测定血根碱对大鼠肠平滑肌细胞收缩的影响。结果表明:酶消化法原代培养的大鼠肠平滑肌细胞纯度高(α–actin检测阳性率达90%以上),密度大,并呈现平滑肌细胞特有的"峰–谷"样排列;血根碱及阿托品可显著抑制肠平滑肌细胞收缩,抑制率分别为32.22%和34.99%;血根碱和阿托品联用对肠平滑肌细胞收缩的抑制率可达68.8%,与单独使用血根碱或阿托品的抑制率差异显著;血根碱对乙酰胆碱、组胺及KCl诱导的肠平滑肌细胞的收缩具有显著的抑制作用;血根碱主要通过作用于细胞膜上的M受体、H1受体和钙离子通道来实现对大鼠肠平滑肌细胞收缩的抑制作用。     

Arachidonic acid and other fatty acids directly activate potassium channels in smooth muscle cells

Arachidonic acid, as well as fatty acids that are not substrates for cyclooxygenase and lipoxygenase enzymes, activated a specific type of potassium channel in freshly dissociated smooth muscle cells. Activation occurred in excised membrane patches in the absence of calcium and all nucleotides. Therefore signal transduction pathways that require such soluble factors, including the NADPH-dependent cytochrome P450 pathway, do not mediate the response. Thus, fatty acids directly activate potassium channels and so may constitute a class of signal molecules that regulate ion channels.     

Localization of calcium pump activity in smooth muscle

A microsomal fraction isolated from longitudinal smooth muscle of guinea pig ileum actively sequesters calcium ion in the presence of magnesium and adenosine triphosphate in a fashion previously described for microsomes of the rabbit aorta. This activity in guinea pig ileum appears to be associated primarily with the plasma membrane as is found in the red cell. By contrast the uptake of calcium in aortic smooth muscle appears to be associated to an appreciable extent with intracellular membranes, possibly analogous to the sarcoplasmic reticulum of skeletal muscle.     

Interleukin-1 mitogenic activity for fibroblasts and smooth muscle cells is due to PDGF-AA

Both interleukin-1 (IL-1) and platelet-derived growth factor (PDGF) induce proliferation of cultured fibroblasts and smooth muscle cells. These polypeptide mediators are released by activated macrophages and other cell types in response to injury and are thought to have a role in tissue remodeling and a number of pathologic processes. Analysis of the kinetics of [3H]thymidine incorporation by cultured fibroblasts demonstrated that the response to IL-1 is delayed approximately 8 hours relative to their response to PDGF. IL-1 transiently stimulated expression of the PDGF A-chain gene, with maximum induction after approximately 2 hours. Subsequent synthesis and release of PDGF activity into the medium was detected as early as 4 hours after IL-1 stimulation, and downregulation of the binding site for the PDGF-AA isoform of PDGF followed PDGF-AA secretion. Antibodies to PDGF completely block the mitogenic response to IL-1. Therefore, the mitogenic activity of IL-1 for fibroblasts and smooth muscle cells appears to be indirect and mediated by induction of the PDGF A-chain gene.     

Ca2+ and Ca2+-activated K+ currents in mammalian gastric smooth muscle cells

Inward movement of calcium through voltage-dependent channels in muscle is thought to initiate the action potential and trigger contraction. Calcium-activated potassium channels carry large outward potassium currents that may be responsible for membrane repolarization. Calcium and calcium-activated potassium currents were identified in enzymatically isolated mammalian gastric myocytes. These currents were blocked by cadmium and nifedipine but were not substantially affected by diltiazem or D600. No evidence for a tetrodotoxin-sensitive sodium current or an inwardly rectifying potassium current was found.     

内皮素A受体在肉鸡肺动脉平滑肌细胞增殖中的作用

为探索内皮素-1(ET-1)对肉鸡肺动脉平滑肌细胞(PASMC)体外增殖的影响及其发挥效应的受体途径,采用四甲基偶氮唑蓝(MTT)比色法观察ET-1对PASMC体外增殖的刺激作用,并分别观察内皮素A受体(ETAR)拮抗剂BQ123和B受体(ETBR)拮抗剂BQ788对ET-1作用下的肉鸡PASMC增殖的影响。结果表明:ET-1可显著刺激肉鸡PASMC的增殖(P<0.05),此效应可被BQ123阻断;BQ788对ET-1刺激的PASMC增殖无显著影响(P>0.05)。结论:ET-1具有促肉鸡PASMC增殖的作用,此作用受ETAR介导。     

植物天然活性产物调控血管平滑肌细胞表型转化研究进展

血管平滑肌细胞(vascular smooth muscle cells,VSMCs)是血管壁的主要构成组分。同时,VSMCs容易受到异常环境信号的影响,发生表型从收缩型向增殖型转化,从而导致以血管平滑肌细胞增生为特征的心血管疾病的发生及发展。因此,寻找调控VSMCs表型转化的天然活性物质,揭示其调控的分子机制非常重要。近年来的研究发现,多种植物天然活性产物可以调控血管平滑肌细胞表型转化,从而为筛选治疗心血管系统疾病的药物研发提供了基础。介绍了VSMCs的特性及其表型转化引起的相关心血管疾病,总结了调控VSMCs表型转化的植物天然活性产物,重点综述了近几年植物天然活性产物调控血管平滑肌细胞表型转化分子机制的研究进展。