Effect of Losartan Therapy on Endothelial Function in Hypertensive Patients

The aim of the study was to evaluate the effect of losartan therapy on endothelial function by measuring serum nitric oxide (NO) levels and urinary excretion of NO in patients with essential hypertension. A group of 30 untreated stage 2 hypertensive patients (15 males and 15 females; age, 51.3 +/- 1.5 years) were included in the study. Office systolic and diastolic blood pressure (BP) was measured by using a mercury sphygmomanometer according to phase I and V of Korotkoff sounds. NO levels in serum and 24-hour urine were determined at baseline and after 6 weeks of daily dosing with losartan (50-100 mg). Losartan therapy resulted in a significant fall in systolic/diastolic BP (from 169.7 +/- 4.1/105 +/- 1.8 mm Hg at baseline to 146 +/- 2.7/91 +/- 1.9 mm Hg at the end of losartan treatment; P < 0.001). The therapy also caused significant increases in both serum NO level (32.74 +/- 3.01 microM/L at baseline versus 79.04 +/- 5.17 microM/L; P < 0.001 after therapy) and urinary NO excretion (58.21 +/- 3.72 microM/L at baseline versus 113.21 +/- 8.63 microM/L; P < 0.001 after therapy). Losartan therapy also reduced serum malondialdehyde (MDA), which is a measure of oxidative stress, by 0.201 nM (15.3%; P = 0.009). Losartan at a dose of 50 to 100 mg per day was effective in reducing elevated BP. The increase in serum NO levels and urinary NO excretion and a decrease in serum MDA levels by losartan treatment indicate a reduction in oxidative stress and enhances NO availability, both of which improve endothelial function. Thus, losartan therapy improves endothelial function in hypertensive patients with essential hypertension.