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An alternative possible formation of diazonium and carbenium ions is through the enzymatic reaction of nitrosamines. [ 5 ] Typical accompanying symptoms during the medical cancer treatment via N -nitroso ureas are the impairment of bone marrow (damage of the stem cell compartment), lymphatic tissue and the gastrointestinal tract.
In 1956, two British scientists, John Barnes and Peter Magee, reported that a simple member of the large class of N-nitrosamines, dimethylnitrosamine, produced liver tumours in rats. Subsequent studies showed that approximately 90% of the 300 nitrosamines tested were carcinogenic in a wide variety of animals. [15]
The effects of nitroso compounds vary dramatically across the gastrointestinal tract, and with diet. Nitroso compounds present in stool do not induce nitrosamine formation, because stool has neutral pH. [7] [8] Stomach acid catalyzes nitrosamine compound formation and is the main location of the reaction during digestion. [9]
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At high doses, it is a "potent hepatotoxin that can cause fibrosis of the liver" in rats. [9] The induction of liver tumors in rats after chronic exposure to low doses is well documented. [ 10 ] Its toxic effects on humans are inferred from animal experiments, but not well-established experimentally.
The mechanisms of carcinogenesis are not completely clear in humans. NMOR and its metabolites may induce DNA damage by directly forming reactive oxygen species or compounds which crosslink DNA. In a rat model in 2013, it was observed that NMOR is hydroxylated, probably by a P450 enzyme, alpha to the N-nitroso moiety. [17]
Among the tobacco-specific nitrosamines, nicotine-derived nitrosamine ketone (NNK) and N-nitrosonornicotine (NNN) are the most carcinogenic. [1] Others include N ′-nitrosoanatabine (NAT) and N-nitrosoanabasine (NAB). NNK and its metabolite 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) are potent systemic lung carcinogens in rats ...
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