Localised alterations in cytoplasmic Ca2+ levels are an integral part of the response of eukaryotic cells to a plethora of external stimuli. Due to the large size of nuclear pores, it has generally been assumed that intranuclear Ca2+ levels reflect the prevailing cytoplasmic Ca2+ levels. Using nuclei prepared from carrot (Daucus carota L.) cells, we now show that Ca2+ can be transported across nuclear membranes in an ATP‐dependent manner and that over 95% of Ca2+ is accumulated into a pool releasable by the Ca2+ ionophore A.23187. ATP‐dependent nuclear Ca2+ uptake did not occur in the presence of ADP or ADPγS and was abolished by orthovanadate. Confocal microscopy of nuclei loaded with dextran‐linked Indo‐1 showed that the initial ATP‐induced rise in [Ca2+] occurs in the nuclear periphery. The occurrence of ATP‐dependent Ca2+ uptake in plant nuclei suggests that alterations of intranuclear Ca2+ levels may occur independently of cytoplasmic [Ca2+] changes.
细胞质 Ca2+ 水平的局部变化是真核细胞对大量外部刺激做出反应的一个组成部分。由于核孔较大,一般认为核内 Ca2+ 水平反映了当时的细胞质 Ca2+ 水平。利用胡萝卜(Daucus carota L.)细胞制备的细胞核,我们现在证明 Ca2+ 能以 ATP 依赖性方式跨核膜运输,并且超过 95% 的 Ca2+ 被积累到一个可被 Ca2+ 离子生成物 A.23187 释放的池中。在存在 ADP 或 ADPγS 的情况下,ATP 依赖性核 Ca2+ 摄取不会发生,而且会被正钒酸盐所取消。装有葡聚糖连接的 Indo-1 的细胞核的共聚焦显微镜显示,最初 ATP 诱导的[Ca2+]上升发生在核外围。植物细胞核中出现的 ATP 依赖性 Ca2+ 摄取表明,核内 Ca2+ 水平的改变可能与细胞质 [Ca2+] 的变化无关。