Activation of skinned trabeculae of the guinea pig induced by laser photolysis of caged ATP.
Activation of skinned trabeculae of the guinea pig induced by laser photolysis of caged ATP.
复制标题
激光光解笼中 ATP 诱导豚鼠去皮小梁的激活。
DOI：
10.1016/s0006-3495(94)80676-9
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发表时间：
1994
影响因子：
3.4
通讯作者：
Barsotti,RJ
中科院分区：
文献类型：
--
作者：
Martin,H;Barsotti,RJ
在Ca2+存在下，通过激光光解笼状ATP，研究了化学剥皮豚鼠小梁的产力动力学。用apyrase对组织进行预孵育，以减少mgadp结合的桥的数量（Martin and Barsotti, 1994）。在未处理的组织中，张力在ATP释放后立即保持不变或略低于严格水平，然后增加到pCa 4.5和5 mM MgATP测量的最大值。同相构件刚度（衡量跨桥附着力）在增加到严密性测量值的55%之前出现了大幅下降。张力的下降速率和上升速率对光解释放ATP的浓度都不敏感。发现刚度下降的速率取决于[ATP]: 1.8 x 10(4) M-1/s-1，比以前在没有Ca2+的类似实验中测量的值高出四倍以上。张力发展速率平均为14.9 +/- 2.5 s-1。用apyrase预孵育改变了收缩早期的机械特性。笼状ATP光解后张力和刚度的初始下降速率和幅度增加，并依赖于[ATP]。张力和刚度初始下降的二阶速率常数分别为8.4 x 10(4) M-1 s-1和1.5 x 10(5) M-1 s-1。这些速率比之前在没有Ca2+的情况下测量的速率快两倍多。apyrase孵育对张力和刚度的时间过程的影响与假设一致，即在僵硬期间，皮肤小梁保留了大量mgadp结合的交叉桥。反过来，这些作用减弱笼状ATP光解后的初始张力下降，并减缓刚性过桥脱离的表观速率。结果还表明，Ca2+增加了未经处理和apyase处理的组织的过桥脱离率，但在未经处理的组织中效果更大。这表明在心肌Ca2+调节过桥脱离的速率。
The kinetics of force production in chemically skinned trabeculae from the guinea pig were studied by laser photolysis of caged ATP in the presence of Ca2+. Preincubation of the tissue during rigor with the enzyme apyrase was used to reduce the population of MgADP-bound cross-bridges (Martin and Barsotti, 1994). In untreated tissue, tension remained constant or dipped slightly below the rigor level immediately after ATP release, before increasing to the maximum measured in pCa 4.5 and 5 mM MgATP. The in-phase component stiffness, which is a measure of cross-bridge attachment, exhibited a large decrease before increasing to 55% of that measured in rigor. Neither the rate of the decline nor of the rise in tension was sensitive to the concentration of photolytically released ATP. The rate of the decline in stiffness was found to be dependent on [ATP]: 1.8 x 10(4) M-1/s-1, a value more than four times higher than that previously measured in similar experiments in the absence of Ca2+. The rate of tension development averaged 14.9 +/- 2.5 s-1. Preincubation with apyrase altered the mechanical characteristics of the early phase of the contraction. The rate and amplitude of the initial drop in both tension and stiffness after caged ATP photolysis increased and became dependent on [ATP]. The second-order rate constants measured for the initial drop in tension and stiffness were 8.4 x 10(4) M-1 s-1 and 1.5 x 10(5) M-1 s-1. These rates are more than two times faster than those previously measured in the absence of Ca2+. The effects of apyrase incubation on the time course of tension and stiffness were consistent with the hypothesis that during rigor, skinned trabeculae retain a significant population of MgADP-bound cross-bridges. These in turn act to attenuate the initial drop in tension after caged ATP photolysis and slow the apparent rate of rigor cross-bridge detachment. The results also show that Ca2+ increases the rate of cross-bridge detachment in both untreated and apyrase-treated tissue, but the effect is larger in untreated tissue. This suggests that in cardiac muscle Ca2+ modulates the rate of cross-bridge detachment.