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MICROBIAL SUCCESSION AND INTESTINAL ENZYME ACTIVITIES IN THE DEVELOPING RAT
Citation:
Chang, J., R. Chadwick, J. Allison, Y. Hayes, D. Talley, AND C. Autry. MICROBIAL SUCCESSION AND INTESTINAL ENZYME ACTIVITIES IN THE DEVELOPING RAT. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/J-95/132.
Description:
The succession of gastrointestinal flora in the developing rat was studied, concomitant with studies of intestinal enzyme activity. Aerobes and anaerobes were identified as members of 4 major bacterial groups, i.e., Lactobacilli spp., Gram positive enterococci, Gram negative rods, consisting mostly of coliforms, and Bacteroides spp. The enzyme activities of nitro and azo reductases, B-glucuronidase, dechlorinase, and dehydrochlorinase were determined by anaerobic incubation of intestinal homogenates with 3,4-dichloronitrobenzene, methyl orange p-nitrophenyl-B-d-glucuronide, and p,p'-DDT respectively. At 7 days of age, no anaerobes were found in either the small or the large intestine of rats. The aerobes detected at this time consisted of lactobacilli, enterococci, and Gram negative rods. From 14 through 35 days, obligate anaerobes, primarily Bacteroides spp., had begun to colonize the large intestine and eventually became the predominant microbe. The nitroreductase activity increased with colonization by anaerobes in both the small and large intestines. Development of azo reductase activity was more erratic. The B-glucuronidase activity, highest at 7 and 14 days, was then drastically reduced in the older pups. This study indicates that the rapid changes in microbial flora and/or intestinal enzyme activity observed here, may alter the susceptibility of pre-pubertal rats to toxicants. Age dependent toxicity may be important in the risk assessment of some environmental chemicals.