Tetrahydrobiopterin induces vasodilation via enhancement of cGMP level

Studies with cell homogenates and cultures had indicated earlier that nitric oxide (NO) synthase is dependent on tetrahydrobiopterin, which apparently functions as a cofactor for the enzyme. The present results showed a vasodilator response to tetrahydrobiopterin in precontracted aorta, which is attained via an increase of the intracellular cyclic GMP level. Furthermore, L-Ng-nitro-arginine-methyl ester inhibits the tetrahydrobiopterin-induced vasodilation, showing the involvement of NO synthase.