Development of an in vitro system combining aqueous and lipid phases as a tool to understand gastric nitrosation

Combet, E. , Preston, T. and McColl, K. (2010) Development of an in vitro system combining aqueous and lipid phases as a tool to understand gastric nitrosation. Rapid Communications in Mass Spectrometry, 24(5), pp. 529-534. (doi:10.1002/rcm.4388)

Combet, E. , Preston, T. and McColl, K. (2010) Development of an in vitro system combining aqueous and lipid phases as a tool to understand gastric nitrosation. Rapid Communications in Mass Spectrometry, 24(5), pp. 529-534. (doi:10.1002/rcm.4388)

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Abstract

Nitrite has long been considered a potential pre-carcinogen for gastric cancer. Acidification of salivary nitrite, derived from dietary nitrate, produces nitrosative species such as NOSCN, NO<sup>+</sup> and N<sub>2</sub>O<sub>3</sub>, which can form potentially carcinogenic N-nitroso compounds. Ascorbic acid inhibits nitrosation by converting the nitrosative species into nitric oxide (NO). However, NO diffuses rapidly to adjacent lipids, where it reacts with oxygen to reform nitrosative species. Nitrosation has been studied in vitro in aqueous systems and less frequently in organic systems; however, there is a need to investigate acid-catalysed nitrosation in a system combining aqueous and lipid environments, hence providing a physiologically relevant model. Here, we describe a two-phase system, which can be used as a tool to understand acid-catalysed nitrosation. Using gas chromatography/ion trap tandem mass spectrometry, we investigated the nitrosation of secondary amines as a function of the lipid phase composition and reaction mixing. An increased interface surface area was a driver for nitrosation, while incorporation of unsaturated fatty acids affected morpholine and piperidine nitrosation differently. Linoleic acid methyl esters did not affect morpholine nitrosation and only had a limited effect on N-nitrosopiperidine formation, while incorporation of free linoleic acid to the lipid phase significantly reduced N-nitrosopiperidine formation, but increased N-nitrosomorpholine formation at low levels. The mechanisms driving these effects are thought to involve amine partitioning, polarity and unsaturated fatty acids acting as scavengers of nitrosating species, findings relevant to the nitrosative chemistry occurring in the stomach, where the gastric acid meets a range of dietary fats which are emulsified during digestion.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Preston, Professor Thomas and Combet Aspray, Dr Emilie and McColl, Professor Kenneth
Authors: Combet, E., Preston, T., and McColl, K.
Subjects:G Geography. Anthropology. Recreation > GE Environmental Sciences
Q Science > QP Physiology
College/School:College of Medical Veterinary and Life Sciences > Institute of Cardiovascular and Medical Sciences
College of Medical Veterinary and Life Sciences > School of Medicine, Dentistry & Nursing
College of Science and Engineering > Scottish Universities Environmental Research Centre
Journal Name:Rapid Communications in Mass Spectrometry
ISSN:0951-4198
ISSN (Online):1097-0231
Published Online:28 January 2010

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