title: Different disappearance rates of plasma nitrite (NO(2)(-)) contribute to apparent steady-state arterio-venous differences in anesthetized animals.
abstract: A possible cause of arterio-venous (A-V) differences in plasma nitrite (NO(2)(-)) levels under steady-state conditions and kinetic features of NO(2)(-) in arterial and venous blood were examined. In isolated rabbit blood, plasma NO(2)(-) in venous blood disappeared faster than that in arterial blood and was accompanied by a concomitant increase in nitrate (NO(3)(-)), implicating oxidation as the main pertinent metabolic pathway. When data were corrected with respective elimination constants and time durations before plasma separation, no A-V difference was estimated under steady-state. Even after these corrections for NO(2)(-) loading in anesthetized rabbits, a large A-V difference in NO(2)(-) levels (arterial venous) was observed, followed by an exponential decrease in NO(2)(-) levels without a reciprocal increase in NO(3)(-) levels. There was a marked difference in NO(2)(-) decay between in vivo and ex vivo experiments, but no increases in the circulating blood were detected for other substances derived from NO(2)(-), such as methemoglobin or low- and high-molecular weight nitrosothiols. In rats and guinea pigs, absence and presence of the A-V difference were detected under steady-state conditions and after NO(2)(-) loading, respectively. These observations indicate that apparent A-V differences under steady-state are artifacts arising from different rates of NO(2)(-) disappearance in arterial versus venous plasma during sample handling, and that tissue compartments may contribute to changes in NO(2)(-) levels in circulating blood. Therefore, caution is required when evaluating plasma NO(2)(-) levels, especially in venous blood.
authors.affiliation: Department of Pharmacology, School of Nursing, Kanazawa Medical University, Uchinada, Ishikawa, Japan. ishitaka@kanazawa-med.ac.jp
authors.forename: Takaharu
authors.initials: T
authors.lastname: Ishibashi
authors.forename: Naoki
authors.initials: N
authors.lastname: Nishizawa
authors.forename: Mihoko
authors.initials: M
authors.lastname: Nakamoto-Nomura
authors.forename: Fusae
authors.initials: F
authors.lastname: Abe
authors.forename: He
authors.initials: H
authors.lastname: Liu
authors.forename: Junko
authors.initials: J
authors.lastname: Yoshida
authors.forename: Tomie
authors.initials: T
authors.lastname: Kawada
authors.forename: Matomo
authors.initials: M
authors.lastname: Nishio
mesh_terms: D000818:Animals; D001158:Arteries / Q000378:metabolism*; D001692:Biological Transport; D006168:Guinea Pigs; D053858:Metabolic Networks and Pathways; D009566:Nitrates / Q000097:blood*; D009573:Nitrites / Q000097:blood*; D010084:Oxidation-Reduction; D011817:Rabbits; D051381:Rats; D017207:Rats, Sprague-Dawley; D014680:Veins / Q000378:metabolism*
chemical_list: D009566:Nitrates; D009573:Nitrites