The American Heart Association and American Council of Cardiology recently updated the guidelines defining hypertension to systolic blood pressure (BP) values >130 mmHg or diastolic BP values >80 mmHg (i.e., Stage 1 hypertension; HTN1). Hypertensive adults classified via the 2003 JNC7 definition (systolic BP >140 mmHg or diastolic BP >90 mmHg) are now categorized as having Stage 2 hypertension (HTN2). Adults with HTN2 exhibit pronounced microvascular dysfunction, one of the first pathophysiological manifestations of the disease. However, the degree to which endothelial dysfunction is evident in the microcirculation of adults meeting the updated definition of hypertension (HTN1) remains equivocal. We tested the hypotheses that microvascular endothelial dysfunction would be present in HTN1 compared to normotensive adults (NTN; systolic BP <120 mmHg and diastolic BP <80 mmHg) but would be less severe compared to HTN2. Endothelium‐dependent dilation (EDD) was retrospectively analyzed in 21 NTN (5 M; 51±1 yrs; resting BP 107±1/68±1 mmHg), 15 HTN1 (6 M; 54±1 yrs; resting BP 126±1/82±1 mmHg), and 37 HTN2 (24 M; 54±2 yrs; resting BP 144±1/93±1 mmHg). Red blood cell flux (laser Doppler flowmetry) was measured during graded intradermal microdialysis perfusion of the endothelium‐dependent agonist acetylcholine (ACh; 10−10–10−1 M). EDD was assessed as flux (perfusion units; PU) and cutaneous vascular conductance (CVC; flux·mmHg−1). Systolic and diastolic BP were significantly different between all three groups (P<0.05 for all). EDD was blunted in both HTN1 and HTN2 relative to NTN when expressed as both flux (NTN: 74±2 vs. HTN1: 60±3 vs. HTN2: 59±2 PU; all P<0.01) and CVC (NTN: 0.86±0.03 vs. HTN1: 0.62±0.04 vs. HTN2: 0.58±0.02 flux·mmHg−1; all P <0.01); however, ACh‐induced dilation was not different between HTN1 and HTN2 (flux P=0.9; CVC P=0.5). These preliminary data suggest that cutaneous microvascular endothelial dysfunction is evident in HTN1 and is as severe relative to HTN2. Future studies are required in order to elucidate the mechanistic mediators of vascular regulation in HTN1.Support or Funding InformationFunding: NHLBI 5R01HL093238‐08, NIA 5T32AG049676‐02This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.