The non specificity of specific nitric oxide synthase inhibitors

L-NAME (N_w-Nitro-L-arginine methylester) and L-NMMA (N^G-Monomethyl-L-arginine, monoacetate) are used widely as nitric oxide (NO) synthase inhibitors. Because of their functional groups (alcohols, amines and carboxylates), it appeared that they could interact with iron in a variety of systems. Using three in vitro models we observed these two compounds had inhibitory effects on cytochrome C reduction by ferrous iron, by ferrous iron accelerated by an unsaturated fatty acid or by epinephrine. This suggests that L-NAME and L-NMMA could have effects in iron containing systems found intracellularly apart from their inhibition of (NO) synthesis.