Synthesis and in vivo distribution of no-carrier-added N(omega)-nitro-L-arginine [C-11]methyl ester, a nitric oxide synthase inhibitor

N(omega)-nitro-L-arginine methyl ester (t-NAME) was labelled with carbon-11 as a potential PET tracer for NO synthase. N(alpha)-t-butoxycarbonyl-N(omega)-nitro-L-arginine was reacted with [C-11]diazomethane. After deprotection with trifluoroacetic acid the formed [C-11]L-NAME was purified using HPLC. Biodistri bution studies in rats and PET studies in monkeys and dogs showed no correlation between radioactivity distribution and NO synthase localization in brain and heart. Substantial amounts of [C-11]methanol were detected in dog plasma shortly after injection. These findings preclude the use of [C-11]L-NAME as a PET tracer.