Transmembrane 45Ca fluxes in isolated smooth muscle cells: basal Ca2+ fluxes.
Transmembrane 45Ca fluxes in isolated smooth muscle cells: basal Ca2+ fluxes.
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分离平滑肌细胞中的跨膜 45Ca 通量：基础 Ca2 通量。
DOI：
10.1152/ajpcell.1984.246.5.c422
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发表时间：
1984
期刊：
影响因子：
--
通讯作者：
Fay,FS
中科院分区：
文献类型：
--
作者：
Scheid,CR;Fay,FS
描述了用于监测悬浮液中平滑肌细胞中45Ca的单向通量的方法。对45 Ca内流数据的房室分析表明，蟾蜍胃肌细胞中的45 Ca交换由两种动力学上可区分的组分组成：相对小的（约100 pmol X cm-2）组分，交换速率快（t1/2约1.4 min）和较大（约930 pmol × cm-2）组分，其交换较慢（t1/2等于87 min）。后者的交换率，但不是前Ca2+池的细胞暴露于升高的K+水平增加，因此，“慢”的吸收组件似乎反映跨膜Ca2+通量，而“快速”的组件可能反映交换的表面结合的标签。与这一解释一致的是，在表面45Ca被迅速和完全置换的条件下，45Ca流出作为一个简单的单指数过程发生，交换速率缓慢（k = 7.80 × 10（-5）s-1）。静息状态下平滑肌细胞跨膜Ca~（2+）通量的表观速率约为0.1 pmol × cm~（-2）× s~（-1）。细胞过程，可能会引起这种幅度的表观跨膜通量率进行了讨论，并提出了一个模型，它似乎描述细胞45 Ca交换在分离的平滑肌细胞。
Methods are described for monitoring unidirectional fluxes of 45Ca in smooth muscle cells in suspension. Compartmental analysis of 45Ca influx data indicate that 45Ca exchange consists of two kinetically distinguishable components in the toad stomach muscle cells: a relatively small (approximately 100-pmol X cm-2) component with a rapid rate of exchange (t1/2 approximately 1.4 min) and a larger (approximately 930-pmol X cm-2) component, which exchanges more slowly (t1/2 congruent to 87 min). The rate of exchange of the latter but not the former Ca2+ pool is increased on exposure of the cells to elevated K+ levels; thus the “slow” component of uptake appears to reflect transmembrane Ca2+ flux, whereas the “rapid” component may reflect exchange of surface-bound label. Consistent with this interpretation is the finding that under conditions in which surface 45Ca is rapidly and completely displaced, 45Ca efflux occurs as a simple monoexponential process with a slow rate of exchange (k = 7.80 X 10(-5) s-1). The apparent rate of transmembrane Ca2+ flux in smooth muscle cells at rest is approximately 0.1 pmol X cm-2 X s-1. Cellular processes that could give rise to an apparent transmembrane flux rate of this magnitude are discussed, and a model is presented which appears to describe cellular 45Ca exchange in the isolated smooth muscle cells.