High salt diet impairs cerebral blood flow regulation via salt-induced angiotensin II suppression.

Abstract

This study sought to determine whether salt-induced ANG II suppression contributes to impaired CBF autoregulation. Cerebral autoregulation was evaluated with LDF during graded reductions of blood pressure. Autoregulatory responses in rats fed HS (4% NaCl) diet vs LS (0.4% NaCl) diet were analyzed using linear regression analysis, model-free analysis, and a mechanistic theoretical model of blood flow through cerebral arterioles. Autoregulation was intact in LS-fed animals as MAP was reduced via graded hemorrhage to approximately 50mm Hg. Short-term (3days) and chronic (4weeks) HS diet impaired CBF autoregulation, as evidenced by progressive reductions of laser Doppler flux with arterial pressure reduction. Chronic low dose ANG II infusion (5mg/kg/min, i.v.) restored CBF autoregulation between the pre-hemorrhage MAP and 50mm Hg in rats fed short-term HS diet. Mechanistic-based model analysis showed a reduced myogenic response and reduced baseline VSM tone with short-term HS diet, which was restored by ANG II infusion. Short-term and chronic HS diet lead to impaired autoregulation in the cerebral circulation, with salt-induced ANG II suppression as a major factor in the initiation of impaired CBF regulation.