This study sought to determine whether salt-induced angiotensin II suppression contributes to impaired cerebral blood flow (CBF) autoregulation.
Cerebral autoregulation was evaluated with laser-Doppler flowmetry during graded reductions of blood pressure. Autoregulatory responses in rats fed high salt (HS; 4% NaCl) diet vs low salt (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 mean arterial pressure (MAP) was reduced via graded hemorrhage to approximately 50 mmHg. Short term (3 days) and chronic (4 weeks) HS diet impaired CBF autoregulation, as evidenced by progressive reductions of laser-Doppler flux with arterial pressure reduction. Chronic low dose angiotensin II infusion (5 mg/kg/min, i.v.) restored CBF autoregulation between the pre-hemorrhage MAP and 50 mm Hg in rats fed short term HS diet. Mechanistic-based model analysis showed a reduced myogenic response and reduced baseline vascular smooth muscle tone with short-term HS diet, which was restored by angiotensin 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. This article is protected by copyright. All rights reserved.