High salt intake delayed angiotensin II-induced hypertension in mice with a genetic variant of NADPH oxidase

Abstract

Background gp91 PHOX, a catalytic subunit of NAD(P)H oxidase, is involved in angiotensin II (Ang II)-induced superoxide (O2 ) generation. This study was designed to examine the hypothesis that an enhancement in O 2 generation due to elevated Ang II induces salt-sensitivity, which contributes to the development of hypertension. Methods Assessment of blood pressure and renal excretory responses to Ang II infusion (2.2 ngmin/g) foR 2 weeks via osmotic minipump was made in knockout (KO; n = 20) mice lacking the gene for gp91 PHOX which were fed on either normal-salt (NS;<0.04% NaCl) or high-salt (HS, 4% NaCl) diet and compared these responses with those in wild-type (WT; n = 23) mice. Results Ang II induced increase in systolic blood pressure (SBP) was started within the 4th day in all groups except in HS fed KO mice in which SBP increased after the 10 th day of Ang II infusion. The increases in SBP were lower in KO than WT mice at the end of 2-week infusion period. In Ang II HS fed KO mice, the urinary excretion rate of nitrite/nitrate (U NOx V) markedly increased but 8-isoprostane excretion rate remained unchanged. These findings indicate that an increase in nitric oxide (NO) with a lack of O2 formation was involved in the delayed hypertension in Ang II HS fed KO mice.ConclusionThese data suggest that an enhanced O2 activity and its interaction with NO contribute to the early developmental phase of Ang II-induced salt-sensitive hypertension. © 2011 American Journal of Hypertension, Ltd.