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TREATMENT OF LONG-EVANS RATS WITH A DEFINED MIXTURE OF DRINKING WATER DISINFECTION BY-PRODUCTS IMPACTS INTESTINAL MICROBIAL METABOLISM.
Citation:
George, S E., G M. Nelson, L R. Brooks, K C. Bailey, M J. Hooth, AND D C. Wolf. TREATMENT OF LONG-EVANS RATS WITH A DEFINED MIXTURE OF DRINKING WATER DISINFECTION BY-PRODUCTS IMPACTS INTESTINAL MICROBIAL METABOLISM. Presented at American Society for Microbiology Meeting, Los Angeles, CA, May 21-25, 2000.
Description:
Water treatment results in the production of numerous halogenated disinfection by-products (DBPs), and has been associated with human colorectal cancer. Because the intestinal microbiota can bioactivate promutagens and procarcinogens, several studies have been done to examine the effect of individual DBPs on intestinal metabolism. However, no studies have been conducted on a defined DBP mixture and the individual chemicals to determine if intestinal effects occur and are additive, antagonistic, or synergistic. Chemicals with well defined or adequately identified modes of action or mechanisms of toxicity were used in this study. Ten week old male Long-Evan rats were treated in their drinking water for 17 weeks with 0.4 g/L potassium bromate, 1.8 g/L chloroform, 0.7 g/L bromodichloromethane (BDCM), 0.07 g/L 3-chloro-4-(dichloromethyl)-5hydroxy-2(5H)-furanone (MX), or a mixture or the four chemicals. Control rats were administered water without additives. Cecal nitroreductase (NR), azoreductase (AR), dechlorinase (DC), Beta-glucuronidase (GLR), P-galactosidase (GAL), and B-glucosidase (GLU) were assayed. No changes in GLU or AR activity were detected in any treatment groups. However, individual chemical treatment significantly elevated or reduced other enzymatic activities. For example, BDCM treatment resulted in reduced DC and GAL activities and elevated NR activity compared to controls. For GAL, GLR, and NR activities, no chemical interactions were observed because mixture treatment effects were not significantly different from controls. However, DC activity in chloroform-, MX-, and BDCM-treated rats was below control levels suggesting that the 3 chemicals were responsible for the reduced activity observed in rats that received the mixture. The small but significant changes in intestinal microbial metabolism suggest that metabolism or bioactivation of chemical co-contaminants may be impacted following exposure to a mixture of DBPs containing chloroform, MX, or BDCM