Study of the stimulus-response relationship in a multi-cellular system by use of stretch-induced contractile activation of vascular tissue.

利用拉伸诱导的血管组织收缩激活来研究多细胞系统中的刺激-反应关系。

基本信息

批准号：
63571051
负责人：
NAKAYAMA Koichi
金额：
$ 1.34万
依托单位：
University of Shizuoka
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1988
资助国家：
日本
起止时间：
1988 至 1989
项目状态：
已结题

项目摘要

The contractile reaction of the vascular smooth muscle in response to mechanical stretch, first observed in isolated segments of canine carotid artery by Bayless in 1902 is often postulated to be a mechanism of myogenic control of blood flow. Studies on stretch-induced tone in vascular tissue touch the core of problems with respect to 1) the mechanisms of transmembrane or cell to cell signal transduction; 2) the interaction between blood and/or endothelium with medial smooth muscle or other vascular components; and 3) the specific role of Ca, i.e., extra- and intracellular Ca components or stretch- sensitive Ca channels. The present experiments were undertaken to elucidate the mechanisms of stretch-induced contraction, with particular reference to the role of Ca and endothelium.Quick stretching of cerebral artery obtained from dog, guinea-pig, rat and cat at a rate of 10 cm/sec to 140% of the slack length of the muscle evoked a delayed contraction, which was always preceded by an incre … More asing cytosolic Ca signals measured by using fura-2. The contraction produced by quick stretch was myogenic in nature, because the response was not affected by autonomic blockers such as phentolamine, propranolol, atropine, or by tetrodotoxin. Furthermore, the contractile response to quick stretch occurred almost equally irrespective of the presence or absence of endothelium, while the endothelium- dependent relaxation produced either by A 23187 in dog or by acetylcholine in cat was abolished when the endothelium was mechanically rubbed from the artery. Hemoglobin (0.01- 0.2 mg/ml), which increased the basal tone by 10-15% of the maximum contracture produced by 80 mM K, potentiated the stretch-induced contraction 2- to 3-fold over the control. The enhanced response to stretch was attenuated by removal of the endothelium and was readily suppressed by Ca antagonists such as nisoldipine as well as diltiazem, indicating that hemoglobin potentiates the contraction upon stretch by promoting transmembrane supply of Ca. The presence of endothelium seems to amplify the vasoconstrictor action of hemoglobin.As to the ionic mechanisms of the stretch-induced tone with special reference to Ca, we also studied whether dual Ca components or stretch-sensitive Ca channel could be dominant in the genesis of the stretch-induced tone. Unlike the contraction produced by high K, which is totally dependent on extracellular Ca, the stretch-induced tone was much more resistant to Ca antagonists and Ca withdrawal. it was necessary to stretch the artery repeatedly in Ca-free medium or in a Ca antagonist-containing medium in order to suppress the stretch-induced tone. Furthermore procaine, dantrolene and ryanodine partially inhibited the tone. Ultramicroscopic studies revealed that in the cerebral artery smooth muscle cells at rest, the pyroantimonate precipitate, an measure of ca was localized along the inner surface of the plasma membrane, while in muscle cells fixed during the stretch- induced contraction the precipitate was diffusely distributed in the myoplasm, indicating that the stretch-induced tone is associated with not only influx of Ca through dihydropyridine-sensitive Ca channel but also Ca release from the inner surface of the plasma membrane.The present results strongly suggest that the genesis of the stretch-induced tone is myogenic in nature. Endothelium seems to modulate the tone, dependent upon the agonistic stimuli applied to the artery. Our studies also suggest that the low susceptibility of the stretch-induced contraction to Ca antagonists is attributable to dual Ca supplies. It is unlikely that a new type of Ca channel, i.e., one which is stretch-sensitive but resistant to Ca antagonist, truly exists in the cerebral artery. Less

1902 年，Bayless 在犬颈动脉的分离部分中首次观察到血管平滑肌对机械拉伸的收缩反应，通常被认为是血管组织中拉伸引起的张力的研究的肌源性控制机制。触及以下问题的核心：1) 跨膜或细胞间信号转导的机制；2) 血液和/或内皮与内侧平滑肌或其他血管成分之间的相互作用；以及3) Ca 的具体作用，即细胞外和细胞内 Ca 成分或拉伸敏感 Ca 通道本实验的目的是阐明拉伸诱导收缩的机制，特别是 Ca 和内皮的作用。将狗、豚鼠、大鼠和猫的脑动脉以 10 厘米/秒的速度拉伸至肌肉松弛长度的 140%，会引起延迟收缩，而延迟收缩总是先于延迟收缩。使用 fura-2 测量的细胞质 Ca 信号增加。快速拉伸产生的收缩本质上是肌源性的，因为该反应不受自主神经阻滞剂（如酚妥拉明、普萘洛尔、阿托品）或河豚毒素的影响。无论是否存在内皮细胞，对快速拉伸的反应几乎同样发生，而狗体内的 A 23187 或当用血红蛋白 (0.01-0.2 mg/ml) 机械摩擦猫体内的乙酰胆碱时，其基础张力增加了 80 mM K 产生的最大挛缩的 10-15%，从而增强了牵张诱导的效果。收缩是对照的 2 至 3 倍，对拉伸的增强反应因内皮的去除而减弱，并且很容易被 Ca2+ 拮抗剂抑制。尼索地平和地尔硫卓，表明血红蛋白通过促进 Ca 的跨膜供应来增强拉伸时的收缩。内皮的存在似乎增强了血红蛋白的血管收缩作用。至于拉伸引起的张力的离子机制，特别参考 Ca。，我们还研究了双 Ca 成分或拉伸敏感 Ca 通道是否在拉伸引起的音调的形成中占主导地位，这与高 K 产生的收缩不同。完全依赖于细胞外 Ca，牵拉引起的张力对 Ca 拮抗剂和 Ca 撤退具有更强的抵抗力，因此有必要在不含 Ca 的介质或含 Ca 拮抗剂的介质中反复牵拉动脉，以抑制牵拉。此外，普鲁卡因、丹曲林和兰尼丁对静息状态的脑动脉平滑肌细胞有部分抑制作用，焦锑酸盐沉淀物沿内表面分布。在质膜上，而在拉伸诱导的收缩过程中固定的肌肉细胞中，沉淀物广泛分布在肌质中，表明拉伸诱导的张力不仅与 Ca2+ 通过二氢吡啶敏感 Ca2+ 通道的流入有关，而且还与 Ca2+ 的释放有关。目前的结果强烈表明，拉伸引起的张力的起源本质上是肌源性的，内皮细胞似乎可以调节张力，这取决于施加于动脉的激动性刺激。还表明，拉伸引起的收缩对 Ca 拮抗剂的低敏感性可归因于双重 Ca 供应。一种新型的 Ca 通道，即对拉伸敏感但对 Ca 拮抗剂具有抵抗力的通道，不太可能真正存在于体内。脑动脉。