Haworth R A, Goknur A B, Biggs A V, Redon D, Potter K T
Department of Anesthesiology, University of Wisconsin, Madison, USA.
Cell Calcium. 1998 Apr;23(4):181-98. doi: 10.1016/s0143-4160(98)90117-8.
Electric field stimulation of adult rat heart cells suspended in medium with 0.2 mM Ca and isoproterenol caused 45Ca uptake at a rate (5.25 pmol/mg/beat) proportional to stimulation frequency. Uptake was strongly inhibited by verapamil or thapsigargin. 45Ca autoradiography showed that stimulation dependent verapamil sensitive uptake was associated with the rod shaped cells, while the uptake by round cells was unaffected by stimulation and was verapamil-insensitive. 45Ca efflux measurements revealed a caffeine-sensitive component of uptake which was abolished by thapsigargin, and a caffeine-insensitive component. Part of the latter was sensitive to thapsigargin but not to 30 s of stimulation; another part was sensitive to such stimulation but not to thapsigargin. With longer times of stimulation, the caffeine-insensitive pool increased in size, part of which appeared to be mitochondrial Ca uptake via a thapsigargin-sensitive pool. The caffeine-sensitive pool labelled quickly in stimulated cells and its size and rate of labelling was increased by stimulation frequency (3.87 pmol/mg/beat), while the caffeine-insensitive pool labelled more slowly and was relatively insensitive to stimulation (0.77 pmol/mg/beat). We conclude that essentially all of the SR Ca pool, as defined by its involvement in excitation-contraction coupling, is released by caffeine.
用0.2 mM钙离子和异丙肾上腺素悬浮培养成年大鼠心脏细胞，电场刺激可引起45Ca摄取，摄取速率（5.25皮摩尔/毫克/搏动）与刺激频率成正比。维拉帕米或毒胡萝卜素可强烈抑制摄取。45Ca放射自显影显示，依赖刺激的维拉帕米敏感摄取与杆状细胞有关，而圆形细胞的摄取不受刺激影响且对维拉帕米不敏感。45Ca外流测量显示，摄取中有一个对咖啡因敏感的成分，该成分被毒胡萝卜素消除，还有一个对咖啡因不敏感的成分。后者一部分对毒胡萝卜素敏感但对30秒刺激不敏感；另一部分对这种刺激敏感但对毒胡萝卜素不敏感。随着刺激时间延长，对咖啡因不敏感的池大小增加，其中一部分似乎是通过对毒胡萝卜素敏感的池进行线粒体钙摄取。对咖啡因敏感的池在受刺激细胞中标记迅速，其大小和标记速率因刺激频率（3.87皮摩尔/毫克/搏动）而增加，而对咖啡因不敏感的池标记较慢且对刺激相对不敏感（0.77皮摩尔/毫克/搏动）。我们得出结论，基本上所有参与兴奋-收缩偶联的肌浆网钙池都可被咖啡因释放。
