Licea H, Walters Marian R, Navar L Gabriel
Department of Physiology, Renal and Hypertension Center of Excellence, Tulane Health Sciences Center, New Orleans, LA 70112, USA.
Acta Physiol Hung. 2002;89(4):427-38. doi: 10.1556/APhysiol.89.2002.4.3.
Accumulation of Angiotensin II (Ang II) in the kidneys of hypertensive rats infused chronically with Ang II occurs by AT1 receptor mediated internalization of Ang II, which may interact with intracellular targets, including nuclear binding sites. The aims of this study were to determine if kidney cell nuclei have specific Ang II binding sites and if chronic infusion of Ang II (70 ng/min; n=9) influences the nuclear Ang II binding capacity. Kidneys were harvested from control and Ang II infused rats and the renal cortexes were homogenized to obtain crude membrane preparations and nuclear fractions. Ang II binding sites were measured with a single point assay by incubating each fraction with 10 nM 125I-Sar-Ile-Ang II in the absence (total binding sites) or presence of either 2.5 M Sar-Leu-Ang II or 25 microM losartan to detect specific AT or AT1 binding sites. Both fractions exhibited specific Ang II binding sites that were displaced by both saralasin and losartan. In control rats, crude membrane preparations had 792 +/- 218 and the nuclear fraction had 543 +/- 222 fmol/mg protein AT1 receptors. AT1 receptor levels in membrane (885 +/- 170 fmol/mg protein) and nuclear fractions (610 +/- 198 fmol/mg protein) were not significantly different in Ang II infused rats. These data support the presence of nuclear Ang II receptors predominantly of the AT1 subtype in renal cells. Chronic Ang II infusion did not alter overall Ang II receptor densities.
长期输注血管紧张素 II（Ang II）的高血压大鼠肾脏中，Ang II 的蓄积是通过 AT1 受体介导的 Ang II 内化作用实现的，该内化作用可能与包括核结合位点在内的细胞内靶点相互作用。本研究的目的是确定肾细胞核是否具有特异性 Ang II 结合位点，以及长期输注 Ang II（70 ng/分钟；n = 9）是否会影响核 Ang II 结合能力。从对照大鼠和输注 Ang II 的大鼠中采集肾脏，将肾皮质匀浆以获得粗膜制剂和核组分。通过单点分析法测量 Ang II 结合位点，即将每个组分与 10 nM 125I - Sar - Ile - Ang II 在不存在（总结合位点）或存在 2.5 M Sar - Leu - Ang II 或 25 μM 氯沙坦的情况下孵育，以检测特异性 AT 或 AT1 结合位点。两个组分均表现出可被沙拉新和氯沙坦取代的特异性 Ang II 结合位点。在对照大鼠中，粗膜制剂具有 792 ± 218 个，核组分具有 543 ± 222 fmol/mg 蛋白的 AT1 受体。在输注 Ang II 的大鼠中，膜（885 ± 170 fmol/mg 蛋白）和核组分（610 ± 198 fmol/mg 蛋白）中的 AT1 受体水平无显著差异。这些数据支持肾细胞中主要存在 AT1 亚型的核 Ang II 受体。长期输注 Ang II 并未改变总体 Ang II 受体密度。
