Endogenous formation of N-nitroso compounds: a current perspective.

Exposure of people to nitrosating agents occurs through multiple pathways, ranging from nitrogen dioxide reactions in the lung to acid-catalysed nitrosation in the stomach to nitrosation mediated by macrophages or bacteria. The use of N-nitrosoproline (NPRO) as an index of endogenous nitrosation has proved to be especially valuable for some of these pathways but may not be universally indicative. Since the development of the NPRO test by Ohshima and Bartsch in 1981, several forms of the test have been used for different purposes. This paper examines some of the issues related to endogenous nitrosation and NPRO and attempts to view the immediate future.