Smith J B, Smith L
Department of Pharmacology, University of Alabama at Birmingham 35294.
J Biol Chem. 1987 Dec 25;262(36):17455-60.
Angiotensin II (ANG II) evoked a rapid efflux of 45Ca2+ which was largely, but not completely, prevented by the removal of extracellular Na+. ANG II had little, if any, effect on a fast component of 45Ca2+ uptake, although the hormone increased a slow component of 45Ca2+ uptake by 2.5-fold. ANG II decreased total cell Ca2+ by about 40% within 1 min of hormone addition. The replacement of extracellular Na+ with N-methyl-D-glucamine or K+ nearly prevented ANG II from decreasing total cell Ca2+. ANG II caused a 5-fold increase in free Ca2+ which reached a peak about 10 s after hormone addition. Free Ca2+ decreased rapidly from the peak to a plateau phase which lasted for several min. Free Ca2+ during the plateau phase was about 1.5 times the basal level. Removing extracellular Na+ caused a more than 2-fold increase in the free Ca2+ concentration that was maintained during the plateau phase, and Na+, added during the plateau phase, rapidly decreased free Ca2+. These findings suggest that the transient nature of the increase in free Ca2+ produced by ANG II is due in part to a net efflux of Ca2+ which is largely dependent on external Na+ and probably mediated by Na+/Ca2+ exchange.
血管紧张素 II（ANG II）引起了 45Ca2+ 的快速外流，去除细胞外 Na+ 可在很大程度上但并非完全阻止这种外流。ANG II 对 45Ca2+ 摄取的快速成分影响很小（如果有影响的话），尽管该激素使 45Ca2+ 摄取的缓慢成分增加了 2.5 倍。添加激素后 1 分钟内，ANG II 使细胞总 Ca2+ 减少了约 40%。用 N - 甲基 - D - 葡糖胺或 K+ 替代细胞外 Na+ 几乎可防止 ANG II 降低细胞总 Ca2+。ANG II 使游离 Ca2+ 增加了 5 倍，在添加激素后约 10 秒达到峰值。游离 Ca2+ 从峰值迅速下降至持续数分钟的平台期。平台期的游离 Ca2+ 约为基础水平的 1.5 倍。去除细胞外 Na+ 导致平台期维持的游离 Ca2+ 浓度增加超过 2 倍，并且在平台期添加 Na+ 会使游离 Ca2+ 迅速降低。这些发现表明，ANG II 产生的游离 Ca2+ 增加的短暂性部分归因于 Ca2+ 的净外流，这在很大程度上依赖于细胞外 Na+，并且可能由 Na+/Ca2+ 交换介导。
