Quantitative relationship between oral nitrate-reducing activity and the endogenous formation of N-nitrosoamino acids in humans.
Salivary nitrate and nitrate concentrations, in vitro kinetics of nitrate reduction in saliva, and numbers of salivary nitrate-reducing micro-organisms were each compared with N-nitrosoamino acid excretion in 16 humans eating controlled diets. N-Nitrosoproline (NPRO) and N-nitrosothiazolidine-4-carboxylic acid (NTCA) excretion were measured after intake of nitrate (5.24 mmol) and L-proline (4.35 mmol) before and after treatment with an oral antiseptic (Peridex, 0.12% chlorhexidine gluconate). Peridex treatment resulted in a 94% reduction in the numbers of salivary nitrate-reducing bacteria, a decline from 17 to 4% in the amount of salivary nitrate that was reduced to nitrite in vivo, and an 85% reduction in the rate of in vitro nitrate reduction by saliva. Concurrently, there were 62 and 74% inhibitions of endogenous NPRO and NTCA formation, respectively. Correlations of the numbers of nitrate reductase micro-organisms, in vivo oral nitrate reduction and salivary nitrite concentrations, with individual NPRO excretion, indicated that individuals with higher oral nitrate-reducing capacities formed more N-nitrosoamino acid endogenously. These data suggest that individual differences in oral nitrate reduction are a significant factor in gastric nitrosation and account for a large proportion of the interindividual variability in nitrosoamino acid excretion.
Shapiro
K B
KB
Institute of Food Science, Cornell University, Ithaca, NY 14853.
Hotchkiss
J H
JH
Roe
D A
DA
D000284:Administration, Oral; D000328:Adult; D002710:Chlorhexidine / Q000031:analogs & derivatives / Q000494:pharmacology; D002849:Chromatography, Gas; D006801:Humans; D008297:Male; D008875:Middle Aged; D009566:Nitrates / Q000008:administration & dosage / Q000378:metabolism*; D009573:Nitrites / Q000737:chemistry; D009602:Nitrosamines / Q000378:metabolism* / Q000652:urine; D009603:Nitroso Compounds / Q000378:metabolism* / Q000652:urine; D012463:Saliva / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism*; D013844:Thiazoles / Q000378:metabolism* / Q000652:urine; D053778:Thiazolidines
D009566:Nitrates; D009573:Nitrites; D009602:Nitrosamines; D009603:Nitroso Compounds; D013844:Thiazoles; D053778:Thiazolidines; C040387:N-nitrosothiazolidine-4-carboxylic acid; C010259:nitrosoproline; C010882:chlorhexidine gluconate; D002710:Chlorhexidine