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PubMed1984

[Influence of ranitidine during a 24-hour period on the level of nitrites, nitrates, nitrosamines and bacterial flora in the gastric juice of healthy subjects].

The aim of this study was to determine the influence of 24 h of ranitidine treatment on gastric bacterial flora and N-nitroso compound formation. Nitrate, nitrite levels, N-nitroso compound concentration were measured and bacterial flora was studied in the fasting and postprandial gastric juice of four healthy men under placebo and ranitidine treatment (150 mg. bid). The pH of seventy-five per cent of the gastric juice samples was over 4 when the patients received their ranitidine treatment. While the mean intragastric concentrations of nitrate, nitrite, N-nitroso compounds and counts of nitrate-reducing organisms were not significantly altered by ranitidine, there was a statistically significant rise in the number of total bacteria. During ranitidine treatment, the nitrite/nitrate ratio was positively correlated with intragastric pH and with the nitrate-reducing organism count of the placebo period. These results suggest that the reduction of nitrate to nitrite required the combination of two factors: a high count of nitrate-reducing organisms before treatment and a high intragastric pH.

Adult↗
PubMed1981

Reactive intermediates from nitrosamines.

Metabolism of N-nitrosodi-n-propylamine by isolated rat liver fractions yielded both n-propanol and isopropanol, providing evidence for a reaction sequence, initiated by formation of the alpha-hydroxynitrosamine, that leads to formation of carbonium ions. Administration of N-nitrosodi-n-propylamine to rats led to formation of 7-n-propylguanine but not 7-isopropylguanine in hepatic DNA, showing that in the intact cell, the reaction sequence is intercepted by nucleophilic sites in DNA before a carbocation is formed. Alkylation of DNA therefore appears to occur primarily by a bimolecular reaction not involving free alkyl cations. N-nitrosodi-n-propylamine is also oxidized by rat liver microsomes by two consecutive beta-oxidation reactions to yield N-nitroso-2-oxopropylpropylamine. The latter agent leads to production of 7-methylguanine and O6-methylguanine in liver DNA following its administration to rats. The chemical nature of the ultimate methylating agent is unclear.

Animals↗
PubMed1983

Assessment of nitrosamine transplacental carcinogenesis in the Syrian golden hamster.

The effects of diethylnitrosamine (DEN) and vinylethylnitrosamine (VEN) in the F1 generation of Syrian golden hamsters are described after the compounds were administered to the P generation during the second half of pregnancy. Morphologic findings revealed that the upper respiratory tract (i.e., trachea) was most affected. VEN appeared highly effective because the first neoplastic alterations (papillary polyps) were seen in both the P and the F1 animals at the 30th postnatal day. The fetal tracheal epithelium also showed chromosomal aberrations after DEN exposure, and VEN enhanced the cloning efficiency of these cells. Combined in vivo - in vitro studies are discussed with special emphasis on the early detection of transformation and neoplastic growth.

Animals↗