Abstract 187: The Absence of Renal ACE Blunts the Renal Response and the Hypertension Induced by Nitric Oxide Synthesis Inhibition

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Abstract

We previously showed that the responses to angiotensin (Ang) II infusion observed in wild type (WT) mice were effectively prevented in mice lacking renal ACE (ACE 3/3 and ACE 10/10 mice) including: hypertension, renal Ang II accumulation, sodium and water retention, and activation of ion transporters in the loop of Henle (NKCC2) and distal nephron (NCC, ENaC, and pendrin). The aim of this study was to test if the absence of renal ACE also protects against hypertension induced by nitric oxide (NO) synthesis inhibition with L-NAME, a low-plasma Ang II hypertension model associated with renal renin-angiotensin system (RAS) activation. In response to L-NAME (0.5 mg/mL in drinking water, 4 wk; n=12-17), systolic blood pressure (SBP) of WT rose from 110±2 to 135±3 mmHg (p<0.01) while SBP in mice lacking renal ACE did not significantly increase: in ACE 10/10, SBP went from 109±3 to 113±2 mmHg (NS), in ACE 3/3 mice from 103±5 to 110±5 mmHg (NS). ACE 10/10 mice exhibited an enhanced natriuretic/diuretic response vs. WT mice: UNaV during the first 24 h of L-NAME was 188±14 μmol in WT and 314±17 μmol in ACE 10/10 (p<0.01). Ang II content [by immunohistochemistry (IHC)] increased from 8±2 to 28±4 % of positive staining/area (p<0.001) in L-NAME-treated WT mice but remained unchanged in ACE 10/10 mice (from 3±1 to 5±1 % of positive staining/area, NS). Consistent with the dissimilar Ang II content, L-NAME increased renal AGT levels by 2.3±0.3 (p<0.01) in WT but not in the ACE 10/10 mice, 0.8±0.1 fold (NS) vs. non-treated animals. The enhanced natriuresis of the L-NAME-treated ACE 10/10 mice was associated with lower NHE3 expression (0.5±0.1 AU) and lower phosphorylation (-P) of NKCC-P (0.48±0.05 AU) and NCC-P (0.5±0.1 AU) vs. equally treated WT (WT defined as 1, p<0.01). In addition, L-NAME-treated WT mice had higher renal macrophage infiltration (82±8 F4/80+ cells/field, by IHC), higher TNF-α content (24±3 pg/mg, by ELISA) and IL-6 (36±2 pg/mg, by ELISA) vs. L-NAME-treated ACE 10/10 (51±3 F4/80+ cells/field, 14±1 pg/mg and 21±1 pg/mg respectively, p<0.01). In conclusion, our results demonstrate that renal ACE plays a fundamental role driving renal responses, hypertension and inflammation induced by NO synthesis inhibition.

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