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Angiotensin II Type 1 Receptor Blockade Corrects Cutaneous Nitric Oxide Deficit in Postural Tachycardia Syndrome
Author(s) -
Stewart Julian Mark,
Taneja Indu,
Medow Marvin S.
Publication year - 2008
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.22.1_supplement.732.1
Subject(s) - losartan , nitric oxide , vasodilation , medicine , angiotensin ii , endocrinology , microdialysis , angiotensin receptor , cardiology , receptor , central nervous system
Low flow postural tachycardia syndrome (POTS), is associated with increased plasma angiotensin‐II (Ang‐II) and reduced neuronal nitric oxide (NO) which decreases NO‐dependent vasodilation. We tested whether the angiotensin‐II type 1 Receptor antagonist losartan would improve NO‐dependent vasodilation in these POTS patients. Further if the action of Ang‐II is dependent on NO, then the NOS inhibitor nitro‐L‐arginine (NLA) would reverse this improvement. We used local heating of the skin of the left calf to 41°C and laser Doppler Flowmetry to assess NO‐dependent conductance (%CVCmax) in 12 low flow POTS patients aged 22.5±8 years and in 15 control subjects aged 22.0±1.3 years. After measuring the baseline local heating response at 3 separate sites, we perfused individual intradermal microdialysis catheters at those sites with losartan 2μg/L, or NLA 10mM, or losartan + NLA. The pre‐drug heat response was reduced in POTS, particularly the plateau phase reflecting NO‐dependent vasodilation. Losartan increased baseline flow in both control and POTS subjects. The baseline increase was blunted by NLA. Losartan increased the POTS heat response to equal the control response (Figure). NLA decreased both control and POTS heat responses to similar conductances. The addition of NLA to losartan reduced control and POTS conductances compared to losartan alone. The data suggest that the reduction in cutaneous nitric oxide dependent vasodilation in low flow POTS is related to angiotensin‐II.