Abstract
The role of the gastrointestinal flora in aromatic nitro-group reduction in vivo and in vitro was investigated in rats. Gut contents, gut wall, and whole liver homogenates exhibited typical specific activities of 22.2, 9.5, and 5.6 µmoles of p-aminobenzoic acid (PABA) formed per g of protein per hr, respectively, from p-nitrobenzoic acid (PNBA). Five strains of normally occurring intestinal bacteria were investigated for nitroreductase activity. A maximum specific activity of 200 µmoles per g of protein per hr for Escherichia coli and a minimum of 87µ moles per g of protein per hr for Aerobacter aerogenes were observed. Urinary excretion of primary amine derivatives during the 48 hr after administration of antibiotics (tetracycline. 50 mg; bacitracin, 50 mg; and neomycin, 100 mg, po) and PNBA (200 mg/kg ip and po) showed an 80-90% decrease as compared to control rats which received no antibiotics. No nitroreductase activity could be detected in the gut contents of antibiotic-treated rats, but hepatic activity was unaffected by the same treatment. These results provide evidence that gastrointestinal bacteria play a major role in the conversion of PNBA to PABA in vivo.
Footnotes
- Received July 16, 1973.
- Copyright © 1974 by The American Society for Pharmacology and Experimental Therapeutics
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