High Salt Enhances ROS and Ang II Contractions of Glomerular Afferent Arterioles From Mice With Reduced Renal Mass

High salt intake, angiotensin II (Ang II), and reactive oxygen species (ROS) enhance progression of chronic kidney disease (CKD). We reported that myogenic contractions of renal afferent arterioles (RAAs) were enhanced by superoxide (O 2 ·- ) generated from p47 phox /NOX2 but inhibited by H 2 O 2 generated from POLDIP2/NOX4. We tested the hypothesis that feeding a high salt diet to mice with the reduced renal mass (RRM) model of CKD generates specific ROS in their RAAs that enhances Ang II contractions. Methods and Results: C57BL/6 mice received surgical RRM or sham operations and 6% or 0.4% NaCl salt for 3 months. Ang II contractions were measured in RAAs perfused at 45 mmHg and superoxide (O 2 ·- ) and H 2 O 2 by fluorescence microscopy. RRM enhanced the gene expression in RAAs for p47 phox and NOX2 and high salt intake in mice with RRM enhanced the gene expression for AT1Rs, POLDIP2 and NOX4 and reduced the gene expression for catalase. Mice with RRM fed a normal salt diet had contractions to 10 -6 mol·l -1 Ang II similar to sham (-56 ± 5 vs -52 ± 5 %; NS). However, RRM mice fed a high salt diet had an enhanced O 2 ·- and H 2 O 2 generation (P<0.005) with Ang II in RAAs and enhanced Ang II maximal contractions (-72 ± 2 vs -45 ± 2%; P<0.005) that were dependent on O 2 ·- from NOX2 since they were prevented in p47 phox -/- mice and on H 2 O 2 from NOX4 since they were prevented in mice with transgenic smooth muscle cell expression of catalase (tg CAT-SMC ), and in POLDIP2 +/- mice. However, RAA contractions to lower concentrations of Ang II (10 -8 to 10 -11 mol·l -1 ) were paradoxically enhanced in tg CAT-SMC vs Wt mice (-17 ± 2 vs -1 ± 1%; P<0.01) and in POLDIP2 +/- vs +/+ mice (-22 ± 3 vs -5 ± 3; P<0.01). Tempol normalized the ROS and Ang II contractions in RAAs from mice with RRM. In conclusion, both O 2 ·- from p47 phox /NOX2 and H 2 O 2 from NOX4/POLDIP2 enhance maximal Ang II contractions of RAAs from mice with RRM fed a high salt diet but H 2 O 2 from NOX4/POLDIP2 reduces the sensitivity to lower concentrations of Ang II by >100-fold and tempol prevents all of these changes Thus, although a high salt intake reduces circulating Ang II, blockade of angiotensin receptors or ROS may prove beneficial for patients with CKD unable to restrict salt.