Influence of the gut microflora on the metabolism of 4-nitrobenzoic acid in the marmoset.

1. 4-Nitrobenzoic acid was metabolized by the marmoset to amino derivatives to the extent of 18.8% (p.o.) and 11.4% (i.p.) of the dose. 2 Reduction of 4-nitrobenzoic acid was significantly decreased by antibiotic pretreatment; the mean decrease in reduction was 81% for animals doses orally and 73% for intraperitoneally dosed marmosets. 3. 4-Nitrohippuric acid was the major metabolite of 4-nitrobenzoic acid, accounting for 30.6% and 49.6% of p.o. and i.p. doses respectively. 4. Antibiotic pretreatment affected the marmosets' normal capacity to reduce 4-nitrobenzoic acid for many weeks after the initial administration. 5. Maximum radioactivity in the blood, after an oral dose, was reached in 30-40 min; the average half-life for the elimination of 4-nitro[carboxy-14C]benzoic acid and its metabolites was 30.4 +/- 3 min after an intramuscular dose. 6. Radioactivity of 4-nitro[carboxy-14C]benzoic acid representing 3.4% of the dose was excreted in rat bile in 24 h.