Arteriovenous Differences in NO₂⁻ Kinetics in Anesthetized Rabbits

Abstract

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.