Arteriovenous differences in NO2- kinetics in anesthetized rabbits.

Despite of the importance of plasma NO2- as an index of endothelial nitric oxide (NO) formation and a substrate for NO production, only a limited kinetic knowledge is available in vivo. To address this issue, we intravenously injected NaNO2 into anesthetized rabbits and quantified changes in arterial and venous plasma NO2- levels. Plasma NO2- levels in arterial blood (956 +/- 220 nM) were slightly, but significantly, higher than those in venous blood (889 +/- 214 nM) under control conditions. Although similar half-lives of the NO2- were observed in arterial and venous plasma, significant arteriovenous differences were observed in the volume of distribution of the central compartment (0.158 +/- 0.007 l/kg in arterial blood and 0.295 +/- 0.015 l/kg in venous blood) and the peripheral compartment (0.259 +/- 0.035 l/kg in arterial blood and 0.135 +/- 0.034 l/kg in venous blood). When NOR1 (authentic NO) was injected, increases in NO2- levels were greater in arterial plasma, and decreases in blood pressure significantly correlated with arterial NO2- levels only (r = 0.90, p < 0.01). These results indicate that changes in NO2- are larger and more easily detectable as an index of NO formation in arterial plasma.