In Vivo Fate of Nitrogenous Air Pollutant Derivatives

摘要

The previously unknown metabolic fate of nitrate and nitrite introduced into the respiratory tract has been studied because they can exist in ambient urban aerosol or be derived from known nitrogenous air pollutants. The detailed study of nitrate and nitrite distribution and chemistry in blood fractions of mice and rabbits has been facilitated by the development of new radiochemical methods. 13NO2- and 13NO3- are cleared rapidly from the lungs in the presence and absence of added carrier. Both penetrate the red cell membrane. The N-13 label from both anions was loosely bound to plasma and cellular proteins but did not form a covalent bond. Nitrate does not undergo detectable reactions in blood. Nitrite is oxidized to nitrate in blood cells and not in plasma. Comparable in vivo and in vitro oxidation rates for mice and rabbits suggest that in vivo oxidation of nitrite and nitrate can be estimated for humans from in vitro blood studies and provide a basis for interspecies extrapolation of NO2 gas toxicity studies. A previously unobserved non-anionic compound or mixture of compounds has been found in blood and is tentatively attributed to metabolic reactions in the gastrointestinal tract where the possibility of forming carcinogenic nitrosamines exists.