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

Bayless于1902年首次在犬颈动脉的离体节段中观察到血管平滑肌响应于机械拉伸的收缩反应，这通常被假定为是血流的肌源性控制机制。对血管组织中牵张诱导的张力的研究触及了以下问题的核心：1）跨膜或细胞到细胞信号转导的机制; 2）血液和/或内皮与中膜平滑肌或其他血管组分之间的相互作用;以及3）Ca的特定作用，即，细胞外和细胞内钙组分或牵张敏感性钙通道。本实验旨在阐明牵张收缩的机制，特别是Ca和内皮的作用。以10 cm/sec的速度快速牵张狗、豚鼠、大鼠和猫的脑动脉至肌肉松弛长度的140%，引起延迟收缩，在此之前总是有一个增加的收缩。在此基础上，我们观察了牵张收缩的机制。结果表明，在牵张收缩过程中，Ca和内皮的作用是非常重要的。 关于我们 用fura-2测定胞浆Ca ~（2+）信号。快速牵拉产生的收缩本质上是肌源性的，因为这种反应不受自主神经阻滞剂如酚妥拉明、心得安、阿托品或河豚毒素的影响。此外，无论是否存在内皮，对快速牵张的收缩反应几乎相同，而当内皮从动脉机械摩擦时，由A23187在狗或乙酰胆碱在猫中产生的内皮依赖性舒张被消除。血红蛋白（0.01- 0.2毫克/毫升），这增加了基础张力的10-15%的最大挛缩产生的80毫米K，加强拉伸引起的收缩2至3倍的控制。增强的响应拉伸减弱去除内皮细胞，并很容易抑制钙拮抗剂，如尼索地平以及地尔硫卓，表明血红蛋白通过促进跨膜供应的钙增强收缩后拉伸。内皮细胞的存在似乎放大了血红蛋白的血管收缩作用。至于牵张诱导张力的离子机制，特别是关于Ca，我们还研究了双Ca组分或牵张敏感性Ca通道是否可以在牵张诱导张力的发生中占主导地位。与完全依赖于细胞外Ca的高K产生的收缩不同，牵张诱导的张力对Ca拮抗剂和Ca撤退更具抵抗力。有必要在无钙培养基或含钙拮抗剂的培养基中反复拉伸动脉以抑制拉伸诱导的张力。此外，普鲁卡因，丹曲洛林和ryanodine部分抑制的音调。超显微镜研究表明，在静止的脑动脉平滑肌细胞中，焦锑酸盐沉淀物，一种钙的量度，沿着质膜的内表面定位，而在牵张诱导收缩期间固定的肌细胞中，沉淀物弥散分布在肌浆中，这表明牵张诱导的张力不仅与通过二氢吡啶的Ca内流有关，敏感的Ca通道，但也从质膜内表面的Ca释放。目前的结果强烈地表明，牵张诱导的张力的起源是肌源性的性质。内皮素似乎调节张力，依赖于施加到动脉的激动性刺激。我们的研究还表明，低敏感性的牵张引起的收缩钙拮抗剂是由于双钙供应。这是不可能的，一种新型的钙通道，即，一种是牵张敏感的，但对Ca拮抗剂有抵抗力，确实存在于脑动脉中。少

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