Wegner F v, Both M, Fink R H A, Friedrich O
Medical Biophysics, Institute for Physiology and Pathophysiology, University of Heidelberg, INF 326, D-69120, Heidelberg, Germany.
J Muscle Res Cell Motil. 2006;27(5-7):315-26. doi: 10.1007/s10974-006-9092-3. Epub 2006 Aug 4.
We examined the effect of clinically relevant doses of thiopental (10-100 microM) on Ca2+ release from the sarcoplasmic reticulum of chemically skinned skeletal muscle fibres of the mouse. Elementary Ca2+ release events (ECRE) were recorded with confocal microscopy and were detected and analysed by an automated algorithm. Thiopental at 25 microM evoked a marked increase in ECRE frequency (events/100 microm/s) from 0.64 +/- 0.32 to 1.56 +/- 0.38 (P < 0.001). Incubation with 5 microM ryanodine significantly reduced spontaneous and evoked ECRE frequencies to 0.08 +/- 0.08 (P < 0.001) and 0.39 +/- 0.25 (25 microM thiopental, P < 0.001) respectively. Thiopental-evoked ECRE show different morphological characteristics compared to spontaneous events. Maximum relative amplitudes (DeltaF/F0)max and spatial width (full width at half maximum) of the events were substantially increased. Full duration at half maximum was increased and some very long events (200 ms compared to approximately 30 ms standard) were produced. The rise times as an indicator of the channel open time were slightly increased. Furthermore, the occurrence of repetitive ECRE was observed. These events, in contrast to previous observations in amphibian skeletal muscle fibres, displayed a multitude of different release patterns. In particular, a repetitive ECRE mode with successively decaying amplitudes was identified and the inter-event intervals were analysed. Estimation of the underlying Ca2+ release current suggests that during repetitive events with a decaying amplitude a decreasing amount of Ca2+ was released within the individual release event. Possible underlying mechanisms are discussed. In summary, thiopental seems to be a potent RyR1 agonist and substantially alters the gating mechanisms of RyR Ca2+ release channel clusters already in clinically relevant doses, i.e. doses administered during general anaesthesia.
我们研究了临床相关剂量的硫喷妥钠（10 - 100微摩尔）对小鼠化学去表皮骨骼肌纤维肌浆网Ca2+释放的影响。通过共聚焦显微镜记录基本Ca2+释放事件（ECRE），并采用自动算法进行检测和分析。25微摩尔的硫喷妥钠使ECRE频率（事件/100微米/秒）从0.64±0.32显著增加至1.56±0.38（P < 0.001）。与5微摩尔的兰尼碱孵育可使自发和诱发的ECRE频率分别显著降低至0.08±0.08（P < 0.001）和0.39±0.25（25微摩尔硫喷妥钠，P < 0.001）。与自发事件相比，硫喷妥钠诱发的ECRE表现出不同的形态特征。事件的最大相对振幅（DeltaF/F0）max和空间宽度（半高全宽）显著增加。半高全宽增加，并且产生了一些非常长的事件（200毫秒，而标准约为30毫秒）。作为通道开放时间指标的上升时间略有增加。此外，观察到了重复性ECRE的发生。与之前在两栖类骨骼肌纤维中的观察结果不同，这些事件表现出多种不同的释放模式。特别地，识别出了一种具有连续衰减振幅的重复性ECRE模式，并对事件间间隔进行了分析。对潜在Ca2+释放电流的估计表明，在振幅衰减的重复性事件中，单个释放事件内释放的Ca2+量逐渐减少。讨论了可能的潜在机制。总之，硫喷妥钠似乎是一种强效的RyR1激动剂，并且在临床相关剂量下，即全身麻醉期间施用的剂量，就已显著改变了RyR Ca2+释放通道簇的门控机制。
