Effects of Tetrahydrobiopterin on Blood Pressure

Tetrahydrobiopterin (BH4) is a cofactor for the nitric oxide (NO) synthase enzymes, such that its insufficiency results in uncoupling of the enzyme, leading to release of superoxide rather than NO in disease states, including hypertension. We hypothesized that oral BH4 will reduce arterial blood pressure (BP) and improve endothelial function in hypertensive subjects. Oral BH4 was given to subjects with poorly controlled hypertension (BP \>135/85 mm Hg) and weekly measurements of BP and endothelial function made. In Study 1, 5 or 10 mg kg-1 day-1 of BH4 (n=8) was administered orally for 8 weeks, and in Study 2, 200 and 400 mg of BH4 (n=16) was given in divided doses for 4 weeks