Twenty healthy subjects were submitted to a hyperglycemic glucose clamp study in which plasma glucose levels were acutely raised to 15 mmol/l (0.33 g/kg as intravenous bolus injection followed by a variable 30% glucose infusion). Mean blood pressure (MBP) was calculated as diastolic plus one-third pulse pressure. Nitrotyrosine was assayed according to Ter Steege et al. (5): the standard curve was constructed with serial dilution of a nitrated protein solution; glucose interference was excluded by performing the ELISA assay of standard solution in the presence of various glucose concentrations (from 10 to 100 mmol/l); the limit of detection of the assay was 10 nmol/l, with intra- and interassay coefficient of variations of 4.5% and 8%, respectively. Nitrotyrosine levels rose steadily during hyperglycemia and remained significantly above baseline at the end of the study. The correlation between nitrotyrosine and MBP increases during the clamp suggests that the two phenomena are related and strictly dependent upon ongoing hyperglycemia. Data are mean ± SD.