Evidence for ENaC involvement in hypertension produced by NOS1 gene deletion in the collecting duct

Abstract

Studies indicate that NOS1 is necessary for proper sodium balance and subsequent blood pressure regulation. We developed collecting duct principle cell‐specific NOS1 knockout (CDNOS1KO) mice using the AQP2‐CRE/LoxP system and found that these mice display a salt‐dependent hypertensive phenotype. We hypothesized that NOS1 in the collecting duct (CD) may regulate the trafficking of the epithelial sodium channel (ENaC) such that CDNOS1KO mice will have greater expression of plasma membrane ENaC in the kidney than flox control mice. Plasma membrane and vesicle fractions from the renal inner medulla of CDNOS1KO and flox control mice were prepared by differential centrifugation and ENaCαβγ expression determined by Western blot analysis. We found a significant increase of ENaCα in the plasma membrane of CDNOS1KO mice (2.0 ± 0.4 RDU/actin, n=4) when compared to flox (1.0 ± 0.2 RDU/actin, n=4, p=0.04). ENaCβγ expression was similar in the plasma membrane from both genotypes as it was for all three subunits in the vesicle fraction. We found that amiloride (3 mg/kg/day ip) significantly lowered the blood pressure in CDNOS1KO on a 4% salt diet (4% salt: 144±2 mmHg; 4% salt + amiloride: 135±0.8 mmHg, n=4, p=0.02). No effects of amiloride on blood pressure were noted in the flox control mice. We conclude that the absence of CD NOS1 leads to an increase of ENaCα in the plasma membrane and may lead to subsequent salt‐sensitive hypertension.