Diffusion coefficients and half-lives of nitric oxide and N-nitroso-L-arginine in rat cortex

In vivo voltammetry was performed in rat brain cortex and in rat brain endothelial constitutive NO-synthase preparations. The use of a recent microcaptor detecting N-hydroxy- and N-nitroso-L-arginine permitted to find only the latest in biological preparations. The construction of a new membrane selective electrode for nitric oxide (NO) allowed to assert its absence in these preparations at micromolar level. Half-live of N-nitroso-L-arginine was 4 s in rat brain cortex and the washout curve of NO after over brain insufflation gave an half-life of 10.5 min; their diffusion coefficients in brain were 3.810(-5) for NO and 3.910(-6) cm2.s-1 for N-nitroso-L-arginine. These facts indicate that N-nitroso-L-arginine is degraded directly into nitrites and citrulline after its synthesis by endothelial NO-synthase.