15N-labelled nitrite/nitrate tracer analysis by LC-MS/MS: Urinary and fecal excretion of nitrite/nitrate following oral administration to mice.

15N-labelled nitrite/nitrate tracer analysis by LC-MS/MS: Urinary and fecal excretion of nitrite/nitrate following oral administration to mice.
Free Radic Biol Med. 2019 Aug 06;:
Authors: Hu CW, Chang YJ, Yen CC, Chen JL, Muthukumaran RB, Chao MR
Abstract
Determination of the modulation of nitrite and nitrate levels in biological samples usually poses a major challenge, owing to their high background concentrations. To effectively investigate the variation of nitrite/nitrate in vivo, in this study, we developed a15N-labelled nitrite/nitrate tracer analysis using LC-MS/MS following the derivatization with 2,3-diaminonaphthalene. This method allows for the determination of 15N-labelled nitrite/nitrate as 15N-2,3-naphthotriazole (15N-NAT) that can efficiently differentiate newly introduced nitrite/nitrate from the background nitrite/nitrate in biological matrices. We also investigated the contribution of background 14N-NAT isotopomers to 15N-NAT, which has long been overlooked in the literature. Our results indicated that the contribution of background 14N-NAT isotopomers to 15N-NAT is significant. Such contribution is constant (∼2.2% under positive ion mode and 1.1% under negative ion mode), and does not depend upon the concentration of 14N-NAT or the sample matrix measured. An equation has been therefore developed, for the first time, to correct the contribution of background 14N-NAT isotopomers to 15N-NAT. With the proposed 15N-lab...

Source: Free Radical Biology and Medicine - August 5, 2019 Category: Biology Authors: Hu CW, Chang YJ, Yen CC, Chen JL, Muthukumaran RB, Chao MR Tags: Free Radic Biol Med Source Type: research