Becker Viola, González-Serratos Hugo, Alvarez Rocío, Bäermann Michael, Irles Claudine, Ortega Alicia
Departamento de Bioquímica, Facultad de Medicina, Universidad Nacional Autónoma de México, México City AP 70-159, CP 04510, México.
J Appl Physiol (1985). 2004 Aug;97(2):467-74. doi: 10.1152/japplphysiol.00906.2003. Epub 2004 Apr 2.
The sarcoplasmic reticulum (SR) Ca(2+) pump is the main homeostatic regulatory mechanism in fast skeletal muscle that maintains intracellular Ca(2+) concentration (Ca(2+)) at the nanomolar level at rest. The transverse tubule (TT) Ca(2+) pump transports cytosolic Ca(2+) to the extracellular space. During prolonged muscular activity, Ca(2+) may increase. TT and SR isolated microsomal vesicles were highly purified, and the purity was checked by immunoblotting. The present study shows the effects of endurance exercise on the activities and structures of the TT and SR Ca(2+) pumps of fast skeletal muscle from rabbit at rest. The Ca(2+) pump activity increased manifolds in TT but did not change in SR. The protein denaturalization profiles obtained by differential scanning calorimetry showed 1) a shift in the transition temperature and an increase in the enthalpy of the TT Ca(2+) pump and 2) a significant change in the transition temperature of the SR Ca(2+) pump Ca(2+)-binding domain. We conclude that the TT Ca(2+) pump activity was upgraded in association with structural changes to handle the changes in Ca(2+) and TT lumen Ca(2+) concentration that occur during endurance exercise.
肌浆网（SR）钙泵是快速骨骼肌中主要的稳态调节机制，可在静息状态下将细胞内钙浓度（[Ca²⁺]i）维持在纳摩尔水平。横管（TT）钙泵将胞质钙转运至细胞外空间。在长时间肌肉活动期间，[Ca²⁺]i可能会升高。高度纯化了分离的TT和SR微粒体囊泡，并通过免疫印迹检查纯度。本研究显示了耐力运动对静息状态下兔快速骨骼肌TT和SR钙泵的活性及结构的影响。TT中的钙泵活性增加了数倍，但SR中的钙泵活性未发生变化。通过差示扫描量热法获得的蛋白质变性图谱显示：1）TT钙泵的转变温度发生偏移且焓增加；2）SR钙泵钙结合结构域的转变温度发生显著变化。我们得出结论，TT钙泵活性随着结构变化而提升，以应对耐力运动期间发生的[Ca²⁺]i和TT管腔钙浓度的变化。
