Alterations of the Intestinal Microflora by Diet, Oral Antibiotics, and Lactobacillus: Decreased Production of Free Amines From Aromatic Nitro Compounds, Azo Dyes, and Glucuronides2

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Abstract
F344 rats were fed compounds containing a nitro, azo, or amine-glucuronide group—2-nitronaphthalene (CAS: 581-89-5), 2-nitrofluorene (CAS: 607-57-8; 2-nitro-9H-fluorene), 4-phenylazo-2-naphthol (CAS: 6410-10-2; 1-[(4-nitrophenyl)azo]-2-naphthol), and 2-naphthylamine-N-d-glucuronide—and the formation of free amines was measured in the feces. The effects of diet (mean vs. grain), administration of antibiotic, and the feeding of Lactobacillus acidophilus were evaluated. Meat-fed rats given 2-nitronaphthalene had approximately 4 times higher concentration of free amines in their feces as compared to the concentration in grain-fed rats. In a similar experiment with 2-naphthylamine-N-d-glucuronide, the meat-fed animals had approximately 1.5 times more of the free amines and 50% less of the conjugates in their feces. When meat-fed animals were given L. acidophilus with 2-nitrofluorene or 2-naphthylamine-N-d-glucuronide, they had significantly lower free amines and higher concentrations of conjugates in their feces than did the meat-fed controls. Similarly, erythromycin or tetracycline decreased the fecal amine production in meat-fed animals that had received 2-nitrofluorene or 4-phenylazo-2-naphthol. In another experiment, erythromycin inhibited the production of free amines from 2-naphthylamine-N-d-glucuronide in rats fed a high-fat diet. Studies of fecal enzymes revealed lower levels of β-d-glucuronidase, nitroreductase, and azoreductase in grain-fed rats and in meat-fed animals also given antibiotics or lactobacilli. These experiments showed that intestinal flora have the ability to convert exogenously administered aromatic nitro and azo compounds and an amine-glucuronide compound to free amines. The rate of these conversions was affected by diet and by oral administration of antibiotics and lactobacilli.