Kinetics of force generation and phosphate release in skinned rabbit soleus muscle fibers.
Kinetics of force generation and phosphate release in skinned rabbit soleus muscle fibers.
复制标题
去皮兔比目鱼肌纤维中力产生和磷酸盐释放的动力学。
DOI：
10.1152/ajpcell.1992.262.5.c1239
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发表时间：
1992
期刊：
影响因子：
--
通讯作者：
Homsher,E
中科院分区：
文献类型：
--
作者：
Millar,NC;Homsher,E
比较了兔比目鱼肌(慢抽动)和腰大肌(快抽动)肌动肌球蛋白-三磷酸腺苷酶(ATPase)循环的力产生和PI释放步骤的动力学。笼状PI[1-(2-硝基)苯乙基磷酸酯]通过激光闪光光解在纤维晶格中快速生成PI。PI在稳定状态下可降低等长张力，但在慢抽动肌肉中的效果不如快抽动肌肉(例如，14 mM PI在慢肌中降低29+/-4.6%，在快肌中降低47+/-5.3%)。慢抽动肌肉对PI浓度突然升高的张力反应有四个阶段，但与快收缩肌肉一样，只有II阶段(力量呈指数下降)似乎是由PI结合跨越桥梁引起的，而其他三个阶段可能是笼式PI光解引起的间接影响。第二相的幅值与PI的稳态减力一致。第二相(Kappa Pi)的比率在20℃时为3.90+/-0.33 S-1，在10℃时为0.28+/-0.02 S-1(1 Mm Pi)。因此，在慢抽动肌肉中，Kappa Pi在20℃时比快肌肉慢33倍，在10℃时慢84倍。与快抽动肌肉相比，慢肌Kappa PI足够慢，足以部分限制ATPase的周转率。
The kinetics of the force generating and Pi release steps of the actomyosin-adenosinetriphosphatase (ATPase) cycle have been compared in Ca(2+)-activated skinned fibers of rabbit soleus (slow twitch) and psoas (fast twitch) muscle. Pi was rapidly photogenerated within the fiber lattice by laser flash photolysis of caged Pi [1-(2-nitro)phenylethyl phosphate]. Pi reduces isometric tension in the steady state but is less effective in slow-twitch muscle than in fast-twitch muscle (e.g., 14 mM Pi reduces tension by 29 +/- 4.6% in slow and by 47 +/- 5.3% in fast). The tension response to a sudden increase in Pi concentration in slow-twitch muscle has four phases, but as in fast-twitch muscle, only phase II (an exponential decline in force) appears to be caused by Pi binding to cross bridges, whereas the other three phases are probably indirect effects caused by caged Pi photolysis. The amplitude of phase II is consistent with the steady-state reduction in force by Pi. The rate of phase II (kappa Pi) is 3.9 +/- 0.33 s-1 at 20 degrees C and 0.28 +/- 0.02 s-1 at 10 degrees C (1 mM Pi). kappa Pi is thus 33 times slower in slow-twitch muscle than in fast at 20 degrees C and 84 times slower at 10 degrees C. In contrast to fast-twitch muscle, in slow muscle kappa Pi is sufficiently slow to partially limit the ATPase turnover rate.