ISOMETRIC FORCE REDEVELOPMENT OF SKINNED MUSCLE-FIBERS FROM RABBIT ACTIVATED WITH AND WITHOUT CA2+
ISOMETRIC FORCE REDEVELOPMENT OF SKINNED MUSCLE-FIBERS FROM RABBIT ACTIVATED WITH AND WITHOUT CA2+
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DOI：
10.1016/s0006-3495(94)80682-4
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发表时间：
1994-11-01
影响因子：
3.4
通讯作者：
HANNON, JD
中科院分区：
文献类型：
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作者：
CHASE, PB;MARTYN, DA;HANNON, JD
测定了兔腰肌甘油纤维在次极大激活和最大激活时的纤维等长张力重建率（k(TR)）。在含有内源性骨骼肌钙蛋白C （sTnC）或用纯化心肌肌钙蛋白C （cTnC）或sTnC重组的纤维中，通过改变[Ca2+]实现了分级激活。一些纤维首先部分地，然后完全地，用一种改良形式的cTnC （aTnC）重建，这种形式能够在没有Ca2+的情况下产生主动力和缩短。k（TR）由张力重建的半衰期得出。在具有内源性sTnC的对照纤维中，k（TR）随[Ca2+]呈非线性增加，在pCa 4.0时k（TR）最大值为15.3 +/- 3.6 s(-1)（平均+/- SD； n = 26次测定25根纤维）。在Ca2+的亚极大激活期间，尽管重构后的最大Ca2+激活力较低（60%），但cTnC重构纤维中的k（TR）比对照快约三倍。为了获得aTnC的亚最大力，对8根纤维进行处理，充分提取内源性sTnC，然后用aTnC和cTnC的混合物（aTnC:cTnC摩尔比1:8.5）重建。第二次提取选择性地去除cTnC。在只含有aTnC的纤维中，力和k（TR）都不受[Ca2+]变化的影响。在pCa 9.2时，力为最大对照的22 +/- 7%（平均+/- SD， n = 15），在pCa 4.0时为24 +/- 8%（平均+/- SD， n = 8），而在pCa 9.2时，k（TR）为最大对照的98 +/- 14%（平均+/- SD， n = 15），在pCa 4.0时为96 +/- 15%（平均+/- SD， n = 8）。单独使用aTnC的纤维最大重建使pCa 9.2时的力增加到最大对照的69 +/- 5%（平均+/- SD， 13根纤维上的n = 22次测定），并使k（TR）减少到最大对照的78 +/- 8%（平均+/- SD， 13根纤维上的n = 22次测定）；Ca2+对力和k（TR）均无显著影响（pCa 4.0）。综上所述，我们解释了我们的结果，表明k（TR）反映了单个细丝调节单位的激活动力学，Ca2+对k（TR）的调制主要受Ca2+与TnC结合的影响。
Fiber isometric tension redevelopment rate (k(TR)) was measured during submaximal and maximal activations in glycerinated fibers from rabbit psoas muscle. In fibers either containing endogenous skeletal troponin C (sTnC) or reconstituted with either purified cardiac troponin C (cTnC) or sTnC, graded activation was achieved by varying [Ca2+]. Some fibers were first partially, then fully, reconstituted with a modified form of cTnC (aTnC) that enables active force generation and shortening in the absence of Ca2+. k(TR) was derived from the half-time of tension redevelopment. In control fibers with endogenous sTnC, k(TR) increased nonlinearly with [Ca2+], and maximal k(TR) was 15.3 +/- 3.6 s(-1) (mean +/- SD; n = 26 determinations on 25 fibers) at pCa 4.0. During submaximal activations by Ca2+, k(TR) in cTnC reconstituted fibers was approximately threefold faster than control, despite the lower (60%) maximum Ca2+-activated force after reconstitution. To obtain submaximal force with aTnC, eight fibers were treated to fully extract endogenous sTnC, then reconstituted with a mixture of aTnC and cTnC (aTnC:cTnC molar ratio 1:8.5). A second extraction selectively removed cTnC. In such fibers containing aTnC only, neither force nor k(TR) was affected by changes in [Ca2+]. Force was 22 +/- 7% of maximum control (mean +/- SD; n = 15) at pCa 9.2 vs. 24 +/- 8% (mean +/- SD; n = 8) at pCa 4.0, whereas k(TR) was 98 +/- 14% of maximum control (mean +/- SD; n = 15) at pCa 9.2 vs. 96 +/- 15% (mean +/- SD; n = 8) at pCa 4.0. Maximal reconstitution of fibers with aTnC alone increased force at pCa 9.2 to 69 +/- 5% of maximum control (mean +/- SD; n = 22 determinations on 13 fibers) and caused a small but significant reduction of k(TR) to 78 +/- 8% of maximum control (mean +/- SD; n = 22 determinations on 13 fibers); neither force nor k(TR) was significantly affected by Ca2+ (pCa 4.0). Taken together, we interpret our results to indicate that k(TR) reflects the dynamics of activation of individual thin filament regulatory units and that modulation of k(TR) by Ca2+ is effected primarily by Ca2+ binding to TnC.