Characterization of angiotensin II-receptor subtypes in podocytes

J Lab Clin Med. 2003 Nov;142(5):313-21. doi: 10.1016/S0022-2143(03)00139-2.


Glomerular podocytes play a key role in maintaining the integrity of the glomerular filtration barrier. This function may be regulated by angiotensin II (Ang II) through activation of cell-surface receptors. Although studies suggest that podocytes express receptors for Ang II, the Ang II binding site has not been characterized with radioligand binding techniques. We therefore used iodine 125-labeled Ang II to monitor Ang II-receptor density during differentiation of a mouse podocyte cell line. Scatchard analyses of equilibrium binding data revealed a single class of high-affinity binding sites (dissociation constant approximately 3 nmol/L) in both differentiated and nondifferentiated cells. During differentiation, the density of Ang II-receptor sites increased roughly 15-fold in differentiated podocytes (maximal density of specific binding sites 881 fmol/mg protein) compared with that in nondifferentiated cells (52 fmol/mg protein; P<.005). Glomerular podocytes expressed messenger RNA for AT1A, AT1B, and AT2 receptor subtypes, and competitive binding studies found that differentiated podocytes expressed mostly AT1 receptors (approximately 75%) with lesser amounts of AT2 (approximately 25%). Up-regulation of Ang II-receptor number was associated with increased Ang II-receptor responsiveness, as evidenced by enhanced Ang II-stimulated inositol phosphate (IP) generation and incorporation of tritiated thymidine. Both [3H]thymidine incorporation and IP generation were mediated by AT1-receptor activation. These data suggest that glomerular podocytes express a high-affinity binding site for Ang II with pharmacologic characteristics of both AT1 and AT2 receptors. This receptor site is up-regulated during podocyte differentiation, and receptor activation induces both IP generation and DNA synthesis by AT1-dependent mechanisms. We speculate that activation of podocyte Ang II receptors contributes to glomerular damage in disease states.

MeSH terms

  • Animals
  • Cell Differentiation / physiology
  • Cell Line, Transformed
  • Epithelial Cells / cytology
  • Epithelial Cells / metabolism*
  • Gene Expression
  • Iodine Radioisotopes
  • Kidney Glomerulus / cytology*
  • Mice
  • Radioligand Assay
  • Receptor, Angiotensin, Type 1 / genetics
  • Receptor, Angiotensin, Type 1 / metabolism*
  • Receptor, Angiotensin, Type 2 / genetics
  • Receptor, Angiotensin, Type 2 / metabolism*


  • Iodine Radioisotopes
  • Receptor, Angiotensin, Type 1
  • Receptor, Angiotensin, Type 2