'Slow' K+-stimulated Ca2+ influx is mediated by Na+-Ca2+ exchange: a pharmacological study.
'Slow' K+-stimulated Ca2+ influx is mediated by Na+-Ca2+ exchange: a pharmacological study.
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“缓慢”K 刺激的 Ca2 流入是由 Na -Ca2 交换介导的：一项药理学研究。
DOI：
10.1016/0005-2736(89)90249-6
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发表时间：
1989
期刊：
影响因子：
--
通讯作者：
Kongsamut,S
中科院分区：
文献类型：
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作者：
Nachshen,DA;Kongsamut,S
在高钾溶液中预去极化15 s后，再加入45 Ca ~（2+），在大鼠脑突触前神经末梢中测量K ~+刺激的45 Ca ~（2+）内流。这种“缓慢”的Ca 2+内流刺激Na+去除，推测介导的Na+单键Ca 2+交换。K+刺激的Ca 2+内流在predepolarized突触体，和Na+去除依赖的Ca 2+内流都是饱和功能的外部Ca 2+浓度，都是半饱和在0.3 mM Ca 2+。20 μM Hg 2+、20 μM Cu 2+或0.45 mM Mn 2+可使两者还原约50%。1 μM Cd ~（2+）、La ~（3+）或Pb ~（2+）对K ~+刺激的和Na ~+去除依赖的Ca ~（2+）内流均无抑制作用，但对未预去极化的突触体，几乎完全抑制K ~+刺激的Ca ~（2+）内流。K+刺激的Ca ~（2+）、Sr ~（2+）或Ba ~（2+）内流在预去极化突触体中的相对渗透性（10：3：1）和相应的Na+清除依赖性二价阳离子摄取的选择性比率（10：2：1）相似。这些结果强烈地表明，K+刺激的“慢”Ca ~（2+）内流在预去极化突触体和Na+清除依赖的Ca ~（2+）内流是由一个共同的机制，Na ~+单键Ca ~（2+）交换介导的。
K+-stimulated45Ca2+influx was measured in rat brain presynaptic nerve terminals that were predepolarized in a K+-rich solution for 15 s prior to addition of45Ca2+. This ‘slow’ Ca2+influx stimulated by Na+removal, presumably mediated by Na+single bondCa2+exchange. The K+-stimulated Ca2+influx in predepolarized synaptosomes, and the Na+-removal-dependent Ca2+influx were both saturating functions of the external Ca2+concentration; and both were half-saturated at 0.3 mM Ca2+. Both were reduced about 50% by 20 μM Hg2+, 20 μM Cu2+or 0.45 mM Mn2+. Neither the K+-stimulated nor the Na+-removal-dependent Ca2+influx was inhibited by 1 μM Cd2+, La3+or Pb2+, treatments that almost completely inhibited K+-stimulated Ca2+influx in synaptosomes that were not predepolarized. The relative permeabilities of K+-stimulated Ca2+, Sr2+or Ba2+influx in predepolarized synaptosomes (10:3:1) and the corresponding selectivity ratio for Na+-removal-dependent divalent cation uptake (10:2:1) were similar. These results strongly suggest that the K+-stimulated ‘slow’ Ca2+influx in predepolarized synaptosomes and the Na+-removal-dependent Ca2+influx are mediated by a common mechanism, the Na+single bondCa2+exchanger.