The investigation of altered Ca2+ handling by the selective modulation of Ca2+ uptake rate of sarcoplasmic reticulum

我们研究了肌浆网（SR）改变的作用，这是已知的心力衰竭心功能障碍的一个原因。我们使用皂素处理的小鼠心脏薄小梁，分别过表达SR-Ca2+ atp酶（SERCA-TG）和肌磷脂（SLN-TG）。Ca2+摄取速率SERCA-TG较快，SLN-TG较慢。最大Ca2+含量、Ca2+诱导的Ca2+释放和Ca2+泄漏在SERCA-TG和SLN-TG中没有改变。在使用Ca2+敏感光蛋白aequorin的乳头肌实验中，SERCA-TG组的峰值张力和Ca2+瞬态峰值振幅升高，SLN-TG组的峰值张力和峰值振幅降低。在SERCA-TG中，张力松弛时间和Ca2+瞬态下降加快，而在SLN-TG中，张力松弛时间延长。因此，我们得出的结论是，选择性调节Ca2+摄取到SR影响Ca2+瞬态和张力的振幅和时间过程，但它不影响最大Ca2+含量，Ca2+诱导的Ca2+释放和Ca2+泄漏。

We investigated the role of the alteration of sarcoplasmic reticulum (SR) which is known to be a cause of cardiac dysfunction in failing heart. We used saponin-treated thin trabeculae obtained from mice hearts with overexpression of SR-Ca2+ ATPase (SERCA-TG) and sarcolipin (SLN-TG), respectively. Ca2+ uptake rate was faster in SERCA-TG and slower in SLN-TG. Maximal Ca2+ content, Ca2+ induced Ca2+ release and Ca2+ leak were not altered in SERCA-TG and SLN-TG. In the papillary muscle experiment using Ca2+ sensitive photoprotein aequorin, peak tension and peak amplitude of Ca2+ transient were increased in SERCA-TG and decreased in SLN-TG. Relaxation time of tension and decline of Ca2+ transient were accelerated in SERCA-TG and prolonged in SLN-TG. Thus, we concluded that selective modulation of Ca2+ uptake into SR influenced the amplitude and time course of Ca2+ transient and tension, however, it did not influence maximal Ca2+ content, Ca2+ induced Ca2+ release and Ca2+ leak of SR.