Determinants of relaxation rate in skinned frog skeletal muscle fibers.
Determinants of relaxation rate in skinned frog skeletal muscle fibers.
复制标题
去皮青蛙骨骼肌纤维松弛率的决定因素。
DOI：
10.1152/ajpcell.1998.274.6.c1608
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发表时间：
1998
期刊：
影响因子：
--
通讯作者：
Rall,JA
中科院分区：
文献类型：
--
作者：
Wahr,PA;Johnson,JD;Rall,JA
在 10°C 下，通过 Ca2+ 螯合剂 diazo-2 的光解快速隔离 Ca2+ 诱导松弛，在剥皮青蛙骨骼肌纤维中检查肌节均匀性和 Ca2+ 浓度对松弛动力学的影响。与完整纤维相比，diazo-2 诱导的弛豫表现出更快、更短的初始慢相和具有更长尾部的快相。在力量发展过程中通过反复释放和再拉伸来稳定肌节，增加了慢相的持续时间并减慢了其动力学。当通过降低 Ca2+ 浓度来降低收缩力时，松弛的整体动力学加速，其中慢相对 Ca2+ 浓度最敏感。抽搐样收缩是由笼中 Ca2+ (DM-Nitrofen) 中的 Ca2+ 光释放引起的，随后 Ca2+ 被完整的肌浆网隔离或 Ca2+ 重新结合到笼中 Ca2+ 上。这些类似抽搐的反应表现出的松弛动力学比在完整纤维中观察到的松弛动力学慢大约两倍。结果表明，松弛的慢速阶段受到肌节均匀程度和 Ca2+ 从细肌丝解离的速率的影响。松弛的快速阶段部分取决于 Ca2+ 激活水平。
The influences of sarcomere uniformity and Ca2+concentration on the kinetics of relaxation were examined in skinned frog skeletal muscle fibers induced to relax by rapid sequestration of Ca2+by the photolysis of the Ca2+chelator, diazo-2, at 10°C. Compared with an intact fiber, diazo-2-induced relaxation exhibited a faster and shorter initial slow phase and a fast phase with a longer tail. Stabilization of the sarcomeres by repeated releases and restretches during force development increased the duration of the slow phase and slowed its kinetics. When force of contraction was decreased by lowering the Ca2+concentration, the overall kinetics of relaxation was accelerated, with the slow phase being the most sensitive to Ca2+concentration. Twitchlike contractions were induced by photorelease of Ca2+from a caged Ca2+(DM-Nitrophen), with subsequent Ca2+sequestration by intact sarcoplasmic reticulum or Ca2+rebinding to caged Ca2+. These twitchlike responses exhibited relaxation kinetics that were about twofold slower than those observed in intact fibers. Results suggest that the slow phase of relaxation is influenced by the degree of sarcomere homogeneity and rate of Ca2+dissociation from thin filaments. The fast phase of relaxation is in part determined by the level of Ca2+activation.