Hypertension is the most important and well established risk factor for atherosclerosis. The vascular and cardiac remodeling present in refractory hypertensive patients are related to endothelial dysfunction, a key factor in early atherogenesis and cardiovascular disease. However the mechanistic relationship among biochemical endothelial function markers, cardiovascular remodeling, and refractory hypertension is unknown. We evaluated the left ventricular mass and function, carotid thickness, and plasma nitrate/nitrite (NO2/NO3), cyclic 3'-5'-guanosine monophosphate (cGMP), and thromboxane B2 (TXB2) levels in refractory hypertensive (RH; n = 20) and healthy (CONTROL; n = 20) subjects 22-65 years old. Carotid thickness, left ventricular mass index (LVMI), and left ventricular fraction ejection (LVFE) were estimated by duplex scan ultrasound. Nitrates/nitrites were assayed using the Griess reaction, and plasma cGMP and thromboxane B2 were determined by enzymatic immunoassay (EIA). Left ventricular mass index was higher in the RH group (138 +/- 20 vs. 108 +/-17 g/m2, p < 0.001) but there was no significant difference in the ejection fraction (67 +/- 5% vs. 69 +/- 4%). Pulse pressure (61 +/- 9 mmHg vs. 46 +/- 10 mmHg) and carotid thickness (1.59 +/- 0.22m vs. 1.04 +/- 0.14mm) were significantly higher (p < 0.001) in RH patients whereas NO2/NO3, cGMP, and thromboxane B2 plasma concentrations were similar in bot groups. There was no association between cardiovascular remodeling and the particular biochemical markers of endothelial function we assessed in refractory hypertensive patients.2525-33