In vivo visualization of the antialbuminuric effects of the angiotensin-converting enzyme inhibitor enalapril.
Angiotensin II modulates cellular functions of podocytes. The aim of this study was to examine the effects of angiotensin II (Ang II) on membrane voltage (Vm) and cytosolic calcium activity ([Ca2+]i) of rat podocytes. To approach better the in vivo situation, we have developed an experimental approach that allows podocytes to be studied in the intact microdissected glomerulus. Ang II depolarized podocytes in the glomerulus (EC50 15 nM, N = 49). Like podocytes in the glomerulus, podocytes in short-term culture also depolarized in response to Ang II (10 nM, N = 5). Ang II increased [Ca2+]i in podocytes in culture (EC50 3 nM, N = 229). In a solution with reduced extracellular [Ca2+] (10 microM), Ang II-mediated [Ca2+]i increase was significantly reduced by 60% +/- 20% (N = 12). Flufenamate, an inhibitor of nonselective ion channels, inhibited Ang II-mediated increase of [Ca2+]i (IC50 20 microM, N = 29). The Ang subtype 1 (AT1) receptor antagonist losartan inhibited both Ang II-mediated depolarization and [Ca2+]i increase in podocytes (N = 5 to 35). Our results support the concept that Ang II might influence podocyte function directly via an AT1 receptor.