Calcium and stretch activation modulate power generation in Drosophila flight muscle.
Calcium and stretch activation modulate power generation in Drosophila flight muscle.
复制标题
DOI：
10.1016/j.bpj.2011.09.034
复制
发表时间：
2011-11
影响因子：
3.4
通讯作者：
Qian Wang;Cuiping Zhao;D. Swank
中科院分区：
文献类型：
--
作者：
Qian Wang;Cuiping Zhao;D. Swank
许多动物通过改变用于运动的肌肉纤维的数量来调节运动的能量产生。然而，具有不同步飞行肌肉的昆虫可能会通过改变钙浓度([Ca~(2+)])来调节飞行所需的功率。在体内，果蝇飞行肌肉中的肌浆钙水平被发现在飞行过程中变化两倍，并与空气动力发电和翅膀拍打频率相关。只有当[Ca~(2+)]还调节飞行肌肉的功率输出和肌肉动力学以符合空气动力学要求时，这种机制才可能实现。我们发现，去皮的果蝇非同步飞行肌肉纤维产生的体外功率随着[Ca~(2+)]的增加而增加。正向肌肉发电开始于PCA=5.8，并在PCA=5.25达到最大值。在这条曲线最陡峭的部分，[Ca~(2+)]的两倍变化导致发电量变化两到三倍，速度变化1.2倍，符合空气动力学要求。为了确定功率变化背后的机制，我们分析了不同水平的[Ca~(2+)]对肌肉纤维延长步骤的张力反应。钙激活的张力和拉伸激活的张力都随着[Ca~(2+)]的增加而增加。然而，钙激活张力饱和时的[Ca~(2+)]略低于拉伸激活张力，当[Ca~(2+)]从Pca=5.7增加到Pca=5.4(可能在飞行中使用的范围)时，拉伸和钙激活张力对总张力增加的贡献率分别为80%和20%。这表明，拉伸激活对[Ca~(2+)]的反应是飞行过程中功率变化的主要机制。
Many animals regulate power generation for locomotion by varying the number of muscle fibers used for movement. However, insects with asynchronous flight muscles may regulate the power required for flight by varying the calcium concentration ([Ca2+]). In vivo myoplasmic calcium levels inDrosophilaflight muscle have been found to vary twofold during flight and to correlate with aerodynamic power generation and wing beat frequency. This mechanism can only be possible if [Ca2+] also modulates the flight muscle power output and muscle kinetics to match the aerodynamic requirements. We found that the in vitro power produced by skinnedDrosophilaasynchronous flight muscle fibers increased with increasing [Ca2+]. Positive muscle power generation started at pCa = 5.8 and reached its maximum at pCa = 5.25. A twofold variation in [Ca2+] over the steepest portion of this curve resulted in a two- to threefold variation in power generation and a 1.2-fold variation in speed, matching the aerodynamic requirements. To determine the mechanism behind the variation in power, we analyzed the tension response to muscle fiber-lengthening steps at varying levels of [Ca2+]. Both calcium-activated and stretch-activated tensions increased with increasing [Ca2+]. However, calcium tension saturated at slightly lower [Ca2+] than stretch-activated tension, such that as [Ca2+] increased from pCa = 5.7 to pCa = 5.4 (the range likely used during flight), stretch- and calcium-activated tension contributed 80% and 20%, respectively, to the total tension increase. This suggests that the response of stretch activation to [Ca2+] is the main mechanism by which power is varied during flight.