Hunt M K, Ramos S P, Geary K M, Norling L L, Peach M J, Gomez R A, Carey R M
Department of Medicine, University of Virginia Health Sciences Center, Charlottesville 22908.
Am J Physiol. 1992 Sep;263(3 Pt 2):F363-73. doi: 10.1152/ajprenal.1992.263.3.F363.
Angiotensin is generated within the kidney, but the precise loci for the formation of angiotensin I (ANG I) and angiotensin II (ANG II) have not been demonstrated. We performed electron microscopy immunocytochemistry in kidney sections of 10-day-old (newborn) and adult Wistar-Kyoto (WKY) rats using specific antibodies to renin, ANG I, ANG II, and angiotensinogen (AO). Renin, ANG I, ANG II, and AO were present in juxtaglomerular (JG) cells. Renin was largely confined to cytoplasmic granules; ANG I and ANG II were colocalized to these granules but also were present in the cytoplasm; AO was distributed throughout the cytoplasm. AO also was present in a renal cortical distribution in proximal tubular cells. Northern blot analysis demonstrated AO mRNA in total kidney and liver but not in renal microvessels. Using the reverse hemolytic plaque assay, we demonstrated release of ANG I and renin from individual renocortical cells of adult WKY rats. Under control conditions, the number of releasing cells was 11 +/- 1 for ANG I and 10 +/- 1 for renin. Addition of rat renin inhibitor (RI) (1 x 10(-5) M), which inhibited renin activity in the medium from 37 to 9 pg ANG I.ml-1.h-1, did not alter ANG I plaque number. Addition of rat AO increased ANG I plaque number to 17 +/- 2 (P less than 0.05). Incubation with both RI and AO prevented the increase in ANG I plaque number obtained with AO alone. Enalapril treatment (7 days; n = 5) increased the number of plaque-forming cells to 22 +/- 2 for ANG I (P less than 0.0005) and to 39 +/- 7 for renin (P less than 0.001). The results suggest an intracellular location for AO and angiotensin and release of renin and ANG I by renal cortical cells and suggest that released angiotensin is produced intracellularly and that secretion of ANG I is augmented by converting enzyme inhibition.
血管紧张素在肾脏内生成，但血管紧张素I（ANG I）和血管紧张素II（ANG II）形成的确切位点尚未得到证实。我们使用针对肾素、ANG I、ANG II和血管紧张素原（AO）的特异性抗体，对10日龄（新生）和成年Wistar-Kyoto（WKY）大鼠的肾脏切片进行了电子显微镜免疫细胞化学研究。肾素、ANG I、ANG II和AO存在于球旁（JG）细胞中。肾素主要局限于细胞质颗粒；ANG I和ANG II共定位于这些颗粒，但也存在于细胞质中；AO分布于整个细胞质。AO在近端肾小管细胞的肾皮质分布中也有存在。Northern印迹分析显示AO mRNA存在于全肾和肝脏中，但不存在于肾微血管中。使用反向溶血空斑试验，我们证实了成年WKY大鼠单个肾皮质细胞释放ANG I和肾素。在对照条件下，ANG I释放细胞的数量为11±1，肾素释放细胞的数量为10±1。添加大鼠肾素抑制剂（RI）（1×10⁻⁵ M），其将培养基中的肾素活性从37 pg ANG I·ml⁻¹·h⁻¹ 抑制至9 pg ANG I·ml⁻¹·h⁻¹，并未改变ANG I空斑数量。添加大鼠AO可使ANG I空斑数量增加至17±2（P＜0.05）。同时用RI和AO孵育可阻止单独使用AO时ANG I空斑数量的增加。依那普利治疗（7天；n = 5）使ANG I形成空斑的细胞数量增加至22±2（P＜0.0005），肾素形成空斑的细胞数量增加至39±7（P＜0.001）。结果提示AO和血管紧张素在细胞内定位，肾皮质细胞释放肾素和ANG I，并提示释放的血管紧张素在细胞内产生，且ANG I的分泌通过转换酶抑制而增加。
