title: The role of oral nitrate in the nitrosation of [14C]proline by conventional microflora and germ-free rats.
abstract: The urinary excretion of N-nitroso-L-[U-14C]proline by conventional microflora and germ free rats was used to assess the role of the gut bacteria and oral nitrate in the endogenous formation of N-nitroso compounds. The formation of nitrosoproline was qualitatively similar in conventional and germfree rats (equivalent to nitrosation of approximately 0.01-0.05% of the initial dose of [U-14C]proline) suggesting no involvement of the intestinal flora in this reaction. Furthermore, nitrosamino acid production was similar following the administration of nitrate and [U-14C]proline or [U-14C]proline alone, demonstrating no involvement of exogenous nitrate under the conditions of the experiment. Dietary contamination with nitrate/nitrite was negligible. The results are consistent with the suggestion that nitrate/nitrite reserves in the body are important in the formation of nitrosoproline in vivo.
mesh_terms: D000284:Administration, Oral; D000818:Animals; D001419:Bacteria / Q000378:metabolism*; D002250:Carbon Radioisotopes; D005856:Germ-Free Life; D007422:Intestines / Q000382:microbiology*; D008297:Male; D009566:Nitrates / Q000378:metabolism*; D009602:Nitrosamines / Q000378:metabolism*; D011392:Proline / Q000378:metabolism*; D051381:Rats; D011916:Rats, Inbred F344; D011919:Rats, Inbred Strains
chemical_list: D002250:Carbon Radioisotopes; D009566:Nitrates; D009602:Nitrosamines; C031618:sodium nitrate; D011392:Proline; C010259:nitrosoproline