Mechanisms of endogenous nitrosation.

Endogenous formation of N-nitroso compounds has been demonstrated in both humans and experimental animals. The extent of this process has been estimated by measurement of urinary N-nitrosoproline and has been shown to be modulated by dietary precursors and inhibitors. It is now also recognized that other (non-gastric) pathways of endogenous nitrosation, including those catalysed by bacteria and mammalian cells, may exist. The mammalian cell catalysed pathway utilizes arginine as a precursor for the nitrosating agent and may occur in macrophages or endothelial cells. The estimated contribution of this pathway to normal basal endogenous nitrosation is approximately 20 nmol of N-nitrosoproline/day.