Dietary sodium intake regulates angiotensin II type 1, mineralocorticoid receptor, and associated signaling proteins in heart

Abstract

Liberal or high-sodium (HS) intake, in conjunction with an activated renin–angiotensin–aldosterone system, increases cardiovascular (CV) damage. We tested the hypothesis that sodium intake regulates the type 1 angiotensin II receptor (AT1R), mineralocorticoid receptor (MR), and associated signaling pathways in heart tissue from healthy rodents. HS (1.6% Na+) and low-sodium (LS; 0.02% Na+) rat chow was fed to male healthy Wistar rats (n=7 animals per group). Protein levels were assessed by western blot and immunoprecipitation analysis. Fractionation studies showed that MR, AT1R, caveolin-3 (CAV-3), and CAV-1 were located in both cytoplasmic and membrane fractions. In healthy rats, consumption of an LS versus a HS diet led to decreased cardiac levels of AT1R and MR. Decreased sodium intake was also associated with decreased cardiac levels of CAV-1 and CAV-3, decreased immunoprecipitation of AT1R–CAV-3 and MR–CAV-3 complexes, but increased immunoprecipitation of AT1R/MR complexes. Furthermore, decreased sodium intake was associated with decreased cardiac extracellular signal-regulated kinase (ERK), phosphorylated ERK (pERK), and pERK/ERK ratio; increased cardiac striatin; decreased endothelial nitric oxide synthase (eNOS) and phosphorylated eNOS (peNOS), but increased peNOS/eNOS ratio; and decreased cardiac plasminogen activator inhibitor-1. Dietary sodium restriction has beneficial effects on the cardiac expression of factors associated with CV injury. These changes may play a role in the cardioprotective effects of dietary sodium restriction.