Midrio M, Danieli-Betto D, Megighian A, Betto R
Institute of Human Physiology, University of Padova, Via Marzolo 3, I-35131 Padova, Italy.
Pflugers Arch. 1997 Aug;434(4):398-405. doi: 10.1007/s004240050413.
The Ca2+ release activity of the sarcoplasmic reticulum (SR) in chemically skinned single slow-twitch fibres from control, 2-day and 7-day denervated rat soleus muscle was studied. Histochemical fibre type composition of the whole muscle, electrophysiological properties and the Ca2+ sensitivity of tension development by single muscle fibres were also studied. All the data were correlated with contractile properties of the in vitro muscle. In the 2-day denervated muscle the SR Ca2+ capacity and the rate of Ca2+ uptake decreased from the control values of 0.384 +/- 0.030 micromol (mg fibre protein)-1 and 19.8 +/- 1.9 nmol min-1 (mg fibre protein)-1, respectively, to 0.210 +/- 0.016 micromol (mg fibre protein)-1 and 13.5 +/- 0.9 nmol min-1 (mg fibre protein)-1; the calculated amount of Ca2+ released upon stimulation by caffeine decreased from the control value of 0.148 to 0.078 micromol (mg fibre protein)-1. In the 7-day denervated muscle, the SR Ca2+ capacity and the rate of Ca2+ uptake increased to 0.517 +/- 0.06 micromol (mg fibre protein)-1 and 21.6 +/- 2.3 nmol min-1 (mg fibre protein)-1, respectively; the calculated amount of Ca2+ released increased to 0.217 micromol (mg fibre protein)-1. Both contraction time and tension of the isometric twitch decreased in 2-day denervated and increased in 7-day denervated muscles. Electrophysiological and histochemical changes, as well as changes in the Ca2+ sensitivity of the muscle fibres did not show any apparent correlation with mechanical changes. It is therefore concluded that the SR plays a prominent role in the early changes of contraction time and tension following denervation.
研究了来自对照、去神经2天和7天的大鼠比目鱼肌的化学去表皮单根慢肌纤维中肌浆网（SR）的Ca2+释放活性。还研究了整块肌肉的组织化学纤维类型组成、电生理特性以及单根肌纤维张力发展的Ca2+敏感性。所有数据均与体外肌肉的收缩特性相关。在去神经2天的肌肉中，SR的Ca2+容量和Ca2+摄取速率分别从对照值0.384±0.030微摩尔（毫克纤维蛋白）-1和19.8±1.9纳摩尔·分钟-1（毫克纤维蛋白）-1降至0.210±0.016微摩尔（毫克纤维蛋白）-1和13.5±0.9纳摩尔·分钟-1（毫克纤维蛋白）-1；咖啡因刺激后计算得出的Ca2+释放量从对照值0.148微摩尔（毫克纤维蛋白）-1降至0.078微摩尔（毫克纤维蛋白）-1。在去神经7天的肌肉中，SR的Ca2+容量和Ca2+摄取速率分别增加至0.517±0.06微摩尔（毫克纤维蛋白）-1和21.6±2.3纳摩尔·分钟-1（毫克纤维蛋白）-1；计算得出的Ca2+释放量增加至0.217微摩尔（毫克纤维蛋白）-1。等长收缩的收缩时间和张力在去神经2天的肌肉中降低，在去神经7天的肌肉中增加。电生理和组织化学变化以及肌纤维Ca2+敏感性的变化与力学变化没有明显相关性。因此得出结论，SR在去神经后收缩时间和张力的早期变化中起重要作用。
