Activated oxygen and mammalian nitrate biosynthesis

Abstract
The oxidation of NH 3 to NO3 -by rat liver in vitro is described. A xanthine-xanthine oxidase reaction also oxidized NH 3 to NO 3 - when H 2 O 2 was added. An in vivo inhibitor of superoxide dismutase enhanced the in vitro liver conversion of NH 3 to NO 3 -. Thus, intracellular oxidation by activated oxygen likely represents the source of endogenously formed NO 3 - in mammals.
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