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

血管平滑肌对机械拉伸的收缩反应是由Bayless于1902年首次在犬颈动脉的分离节段中观察到的，通常被认为是肌源性控制血流的一种机制。血管组织拉伸张力的研究涉及以下几个方面的核心问题：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；3)钙的特定作用，即细胞外和细胞内钙组分或拉伸敏感钙通道。本实验旨在阐明拉伸诱导收缩的机制，特别是钙和内皮的作用。将狗、豚鼠、大鼠和猫的大脑动脉以10厘米/秒的速度快速拉伸至肌肉松弛长度的140%，可引起延迟收缩，在此之前总是有增加的细胞质Ca信号。快速拉伸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，无论内皮存在与否，对快速拉伸的收缩反应几乎相同，而当机械摩擦内皮时，狗的A 23187或猫的乙酰胆碱产生的内皮依赖性松弛被消除。血红蛋白（0.01- 0.2 mg/ml）使基底张力增加了80 mM K产生的最大收缩的10-15%，使拉伸引起的收缩比对照组增强了2- 3倍。对拉伸的增强反应通过去除内皮而减弱，并且很容易被钙拮抗剂如尼索地平和地尔硫卓所抑制，这表明血红蛋白通过促进钙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。对于拉伸致音的离子机制，特别是钙离子，我们还研究了双钙组分或拉伸敏感钙通道在拉伸致音的发生中是否占主导地位。与完全依赖于细胞外钙的高钾引起的收缩不同，拉伸引起的张力对钙拮抗剂和钙戒断更有抵抗力。在无Ca介质或含Ca拮抗剂介质中反复拉伸动脉以抑制拉伸引起的张力。此外，普鲁卡因、丹曲林和瑞诺定部分抑制张力。超微显微镜观察发现，在静止的大脑动脉平滑肌细胞中，焦锑酸盐沉淀，沿质膜内表面有一定的ca分布，而在拉伸收缩时固定的肌肉细胞中，焦锑酸盐沉淀在肌浆中弥漫性分布。表明拉伸引起的张力不仅与钙通过二氢吡啶敏感的钙通道内流有关，还与钙从质膜内表面释放有关。目前的结果强烈表明，拉伸引起的张力在本质上是肌源性的。内皮细胞似乎调节张力，依赖于应用于动脉的激动性刺激。我们的研究还表明，拉伸引起的收缩对钙拮抗剂的低敏感性可归因于双钙供应。脑动脉中不太可能真正存在一种新型的钙通道，即对钙拮抗剂具有拉伸敏感性但对钙拮抗剂具有耐药性的钙通道。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