Haller H, Lindschau C, Quass P, Luft F C
Franz Volhard Clinic and the Max Delbrück Center for Molecular Medicine, Humboldt University of Berlin, Germany.
J Am Soc Nephrol. 1999 Jan;10 Suppl 11:S75-83.
Angiotensin II (AngII) is present inside vascular smooth muscle cells (VSMC); however, its intracellular functions, if any, are unknown. AngII was administered by microinjection. AngII was identified in endosomes and in the nucleus. Microinjection of AngII (10(-10) M) led to a rapid increase in the intracellular Ca2+ concentration ([Ca2+]i) in the cytosol and in the nucleus. The [Ca2+]i increase was the result of an influx of extracellular Ca2+ ions. The intracellular AngII effect was totally inhibited by concomitant injection of the AngII type 1 receptor blocker candesartan. Desensitization of extracellular AngII receptors, on the other hand, did not influence the intracellular effects, and neither did extracellular candesartan. The increase in [Ca2+]i was observed not only in the microinjected cell but also in directly adjacent VSMC. In contrast to the microinjected cells, the [Ca2+]i increase in the adjacent cells was mostly the result of Ca2+ release from intracellular stores. Pretreatment with thapsigargin, which interferes with Ca2+ release from intracellular stores, abolished the AngII response in adjacent cells. Microinjection of inositol trisphosphate induced a [Ca2+]i response in adjacent cells that was similar to the AngII-induced effects. Preincubation of VSMC with uncoupling substances did not decrease the AngII response but prevented a [Ca2+]i surge in adjacent cells. Tyrosine phosphorylation was next examined. Phosphorylation was detected in the injected cells, primarily in the cytoskeleton. It can be concluded that intracellular AngII binds to intracellular AngII receptors and elicits increased [Ca2+]i in the injected cell and then in cells in the immediate neighborhood. Cell-cell contact is necessary for the AngII-mediated effects. These data suggest that intracellular AngII may stimulate a cluster of VSMC from a single cell, via the release of second messengers.
血管紧张素II（AngII）存在于血管平滑肌细胞（VSMC）内；然而，其细胞内功能（如果有的话）尚不清楚。通过微量注射给予AngII。在内体和细胞核中鉴定出了AngII。微量注射AngII（10^(-10) M）导致细胞质和细胞核内细胞内Ca2+浓度（[Ca2+]i）迅速增加。[Ca2+]i的增加是细胞外Ca2+离子内流的结果。同时注射1型血管紧张素II受体阻滞剂坎地沙坦可完全抑制细胞内AngII的作用。另一方面，细胞外AngII受体的脱敏并不影响细胞内作用，细胞外坎地沙坦也不影响。不仅在微量注射的细胞中观察到了[Ca2+]i的增加，而且在直接相邻的VSMC中也观察到了。与微量注射的细胞相比，相邻细胞中[Ca2+]i的增加主要是细胞内储存库释放Ca2+的结果。用毒胡萝卜素预处理可干扰细胞内储存库释放Ca2+，从而消除相邻细胞中的AngII反应。微量注射肌醇三磷酸可在相邻细胞中诱导与AngII诱导效应相似的[Ca2+]i反应。用解偶联物质对VSMC进行预孵育不会降低AngII反应，但可防止相邻细胞中[Ca2+]i的激增。接下来检测酪氨酸磷酸化。在注射的细胞中检测到磷酸化，主要在细胞骨架中。可以得出结论，细胞内AngII与细胞内AngII受体结合，在注射的细胞中引发[Ca2+]i增加，然后在紧邻的细胞中引发增加。细胞间接触对于AngII介导的效应是必要的。这些数据表明，细胞内AngII可能通过释放第二信使从单个细胞刺激一群VSMC。
