Characterization of angiotensin II-receptor subtypes in podocytes.

Journal Article

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.

Full Text

Duke Authors

Cited Authors

  • Wang, L; Flannery, PJ; Spurney, RF

Published Date

  • November 2003

Published In

Volume / Issue

  • 142 / 5

Start / End Page

  • 313 - 321

PubMed ID

  • 14647035

International Standard Serial Number (ISSN)

  • 0022-2143

Digital Object Identifier (DOI)

  • 10.1016/S0022-2143(03)00139-2

Language

  • eng

Conference Location

  • United States