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背景:肌丝牵拉实验是检验去神经后的肌丝标本在不同受力负荷状态下的肌肉自身力学变化的实验方法。目的:探讨不同前负荷平滑肌组织在肌动图上产生的自主性舒缩波形特点以及自主性舒缩时的膜电流特点。方法:平滑肌肌丝取自昆明小鼠主动脉平滑肌层及膀胱壁肌层。肌丝标本松弛状态下在任氏液中稳定5 min后将两端固定,微量步进定位器调整标本长度,使前负荷至1 g。以此作为标本初长度(L0)。微量器快速牵拉标本1次(L0+1)即低前负荷,每间隔5min快速牵拉标本1次,第10次为高负荷(L0+10),在快速牵拉前滴加3%Ca Cl2及0.05%Nitrendipine干预,观察L0+1及L0+10后标本的自主舒缩。制备2μm玻璃微电极,显微镜下贴附平滑肌组织并高阻封接,测量L0+1及L0+10两种前负荷后应力松弛时间相的膜电位变化。结果与结论:(1)平滑肌标本应力松弛期随前负荷上升而变短,且膀胱平滑肌张力松弛期短于主动脉平滑肌,显示两种组织在顺应性上存在差异;(2)应力松弛期自主舒缩幅度随前负荷的增加而加大;(3)主动脉平滑肌膜电流波动随前负荷的增加而显著;(4)高钙环境显著提高了主动脉平滑肌膜电流的幅度及频率,这可被L-型钙通道阻断剂(0.05%Nitrendipine)抑制而减弱;(5)结果提示,前负荷的增长会引起应力松弛期肌源性自主收缩加强,这种顺应性变化与机械性牵拉引起的跨膜离子流动有关。高负荷状态下的高钙环境引起平滑肌膜电流的加强,这种变化可被L-型钙通道阻断剂所抑制。从而说明快速牵拉不仅直接作用于平滑肌机械门控通道,同时也影响到L-型钙通道的激活。
Background: Myofilament traction test is an experimental method to test the mechanical changes of muscle after denervation myofilament specimens under different stress conditions. OBJECTIVE: To investigate the characteristics of spontaneous contraction and contraction of different pre-loaded smooth muscle tissues and their membrane currents during spontaneous contraction and contraction. Methods: Smooth muscle myofilament was taken from the aortic smooth muscle layer and bladder wall muscle of Kunming mice. Myofilament specimens were allowed to stabilize in either Ringer’s solution for 5 min after the specimen was loosened. Both ends were fixed and the micro-stepping positioner was used to adjust the length of the specimen so that the pre-load was 1 g. This sample as the initial length (L0). (L0 + 1), ie, low preload, rapidly pulling the specimen once every 5 minutes, the tenth time being the high load (L0 + 10), dropping 3% Ca Cl2 and 0.05% Nitrendipine intervention, observation of L0 + 1 and L0 +10 autologous contraction. A 2μm glass microelectrode was prepared. The smooth muscle tissue was attached under the microscope and sealed with high resistance. The changes of membrane potential during stress relaxation phase after L0 + 1 and L0 + 10 pre-stress were measured. RESULTS AND CONCLUSION: (1) The stress relaxation period of smooth muscle specimens became shorter with the increase of the former load, and the duration of tension relaxation in the bladder smooth muscle was shorter than that of the aortic smooth muscle. There was a difference in compliance between the two tissues. (2) (3) Aortic smooth muscle membrane current fluctuations with the increase of the former load significantly; (4) High calcium environment significantly increased the aortic smooth muscle current amplitude and frequency, which can be Was inhibited by L-type calcium channel blockers (0.05% Nitrendipine) and weakened; (5) The results suggest that the increase in preload will cause relaxation of muscle relaxation during autonomic contraction, this compliance changes and mechanical stretch Caused by transmembrane ion flow related. The high calcium environment at high load conditions results in a potentiation of the smooth muscle membrane current, which can be suppressed by L-type calcium channel blockers. Thus, the rapid pull not only directly affects the mechanical channel of smooth muscle, but also affects the activation of L-type calcium channel.