gms | German Medical Science

Angiotensin (Ang) II enhances renal sympathetic neurotransmission and stimulates NO release. The present study investigates whether Ang II mediated modulation of sympathetic neurotransmission is dependent on NO production in the kidney. AT2 -/y receptor deficient mice are used to identify the Ang II receptor subtype involved. Mice kidneys were isolated and perfused with Krebs-Henseleit solution. Drugs were added to the perfusion solution in a cumulative manner. Release of endogenous norepinephrine (NE) was measured by HPLC. AT1-receptor expression was analysed by real time PCR. Ang II (0.01 nM - 30 nM) dose dependently increased pressor responses in kidneys of AT2 -/y mice and wild type (AT2 +/y) mice. Maximal pressor responses and EC50 values for Ang II and NE were greater in AT2 -/y than in AT2 +/y mice. L-NAME (0.3 mM) enhanced Ang II induced pressor responses in both strains. In AT2 -/y mice Ang II induced facilitation of NE release was more pronounced than in AT2 +/y mice. L-NAME reduced Ang II mediated facilitation of NE release in both strains. This reduction was more potent in AT2 -/y mice. In kidneys of AT2 -/y mice the AT1 receptor expression was upregulated. These results suggest that activation of AT1 receptors by Ang II releases NO in mouse kidney to modulate sympathetic neurotransmission. Since AT1 receptors are upregulated in AT2 -/y mice kidneys, NO dependent effects were greater in these mice. Thus, NO seems to play an important modulatory role for renal sympathetic neurotransmission.