Hartl C, Fischer S, Hasselbach W
Max-Planck-Institut für Medizinische Forschung, Abteilung für Physiologie, Heidelberg, Bundesrepublik Deutschland.
Z Naturforsch C J Biosci. 1990 Jan-Feb;45(1-2):121-4. doi: 10.1515/znc-1990-1-221.
Enzymatically isolated myocytes from adult rats were used to measure 45Ca-uptake from salt media of reduced Ca2(+)-content (0.1 mM) with normal (4 mM) or elevated (20 mM) potassium concentrations. Ca2(+)-uptake was interrupted by filtration followed by rapid chasing the filter with salt solutions containing no Ca2+, 2 mM Ca2+ or 2 mM La3+. Rate and extent of 45Ca-uptake of resting cells were found to be 3-fold enhanced when chasing was performed with La3(+)-containing media. In contrast La3+ does not affect Ca2(+)-exchange of depolarized cells, the fluxes of which approximate rates sufficiently high for contraction activation and that are sensitive to Ca2(+)-channel blockers. The effect of La3+ on resting cells suggests the existence of a small rapidly exchanging La3(+)-sensitive Ca2(+)-compartment located adjacent to the plasma membrane. This compartment is though to be either closed or has become La3(+)-insensitive in activated cells. The subsarcolemmal cysternae of the SR, the so-called "peripheral couplings" are most likely the morphological substrate of this compartment.
从成年大鼠中酶解分离出的心肌细胞，用于测量在钙离子含量降低（0.1 mM）、钾离子浓度正常（4 mM）或升高（20 mM）的盐培养基中的45Ca摄取量。通过过滤中断Ca2+摄取，随后用不含Ca2+、含2 mM Ca2+或2 mM La3+的盐溶液快速冲洗滤膜。当用含La3+的培养基进行冲洗时，静息细胞的45Ca摄取速率和摄取量提高了3倍。相比之下，La3+不影响去极化细胞的Ca2+交换，去极化细胞的通量接近足以激活收缩的速率，并且对Ca2+通道阻滞剂敏感。La3+对静息细胞的作用表明，在质膜附近存在一个小的、快速交换的、对La3+敏感的Ca2+区室。这个区室在活化细胞中要么关闭，要么对La3+不敏感。肌浆网的肌膜下池，即所谓的“周边连接”，很可能是这个区室的形态学基础。
