title: Specific receptor for angiotensinogen on human renal cells.
abstract: BACKGROUND
  We recently demonstrated the existence of an angiotensinogen (AGT) receptor on placental cells. It has been established that there is a tissue-specific renin-angiotensin system (RAS) in the human kidney. This study focused on whether human renal proximal tubule epithelial cells possessed an AGT receptor.
  
  
  METHODS
  Human renal proximal tubule epithelial cells were cultured in plastic wells. Binding assays were carried out by adding iodinated angiotensinogen ((125)I-AGT) to each culture well, with or without unlabeled AGT. The cells were washed, lysed, and the radioactivity was measured.
  
  
  RESULTS
  Human renal proximal tubule epithelial cells bound (125)I-AGT in a time-dependent manner. This binding was competitively and specifically inhibited by unlabeled AGT. Bound (125)I-AGT was competitively displaced by AGT. Acid washing removed 30% at 8 h, indicating that 70% bound AGT had been internalized. Scatchard plot binding analysis showed that the identified AGT receptor possessed a single class of high-affinity binding sites (K(d)=1.73 nmol, B(max)=23.39 pmol/10(6) cells).
  
  
  CONCLUSIONS
  The results of this study provide evidence for the presence of an AGT receptor on human renal proximal tubule epithelial cells. Our finding suggests that the AGT receptor may be an integral component of the renal RAS.
authors.affiliation: Marshfield Clinic Research Foundation, 1000 North Oak Avenue, Marshfield, WI 54449, USA.
authors.forename: Nan
authors.initials: N
authors.lastname: Pan
authors.forename: Jiangming
authors.initials: J
authors.lastname: Luo
authors.forename: Steven J
authors.initials: SJ
authors.lastname: Kaiser
authors.forename: Wayne L
authors.initials: WL
authors.lastname: Frome
authors.forename: Richard A
authors.initials: RA
authors.lastname: Dart
authors.forename: Duane A
authors.initials: DA
authors.lastname: Tewksbury
mesh_terms: D000803:Angiotensin I / Q000378:metabolism; D000804:Angiotensin II / Q000378:metabolism; D000808:Angiotensinogen / Q000097:blood / Q000378:metabolism*; D001667:Binding, Competitive; D002478:Cells, Cultured; D004847:Epithelial Cells / Q000166:cytology / Q000378:metabolism*; D006801:Humans; D007457:Iodine Radioisotopes; D007684:Kidney Tubules / Q000166:cytology / Q000378:metabolism*; D011945:Receptors, Angiotensin / Q000378:metabolism*; D013997:Time Factors
chemical_list: D007457:Iodine Radioisotopes; D011945:Receptors, Angiotensin; D000808:Angiotensinogen; D000804:Angiotensin II; D000803:Angiotensin I