You are here:
CHANGES IN THE CECAL MICROBIAL METABOLISM OF RATS INDUCED BY INDIVIDUAL AND A MIXTURE OF DRINKING WATER DISINFECTION BY-PRODUCTS
Citation:
George, S E., L R. Brooks, D C. Wolf, G M. Nelson, K C. Bailey, AND M J. Hooth. CHANGES IN THE CECAL MICROBIAL METABOLISM OF RATS INDUCED BY INDIVIDUAL AND A MIXTURE OF DRINKING WATER DISINFECTION BY-PRODUCTS. CANCER LETTERS 204(1):15-21, (2004).
Description:
ABSTRACT
Water treatment results in the production of numerous halogenated disinfection byproducts (DBPs), and has been associated with human colorectal cancer. Because the intestinal microbiota can bioactivate xenobiotics, 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 if these are additive, or greater or less than additive. Chemicals with well defined or adequately identified modes of action or mechanisms of toxicity were used in this study. Ten week old male Long-Evans (Eker) 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)-5-hydroxy-2(5H)-furanone (MX), or a mixture of the four chemicals. Control rats were administered water without additives. Cecal nitroreductase (NR), azoreductase (AR), dechlorinase (DC), -glucuronidase (GLR), -galactosidase (GAL), and -glucosidase (GLU) were assayed. No change in GLU or GLR activity was detected in any treatment group. However, individual chemical treatment significantly elevated or reduced other enzymatic activities. BDCM treatment resulted in reduced DC and GAL activities and elevated NR and AR activity compared to controls. For GAL, AR, arid NR activities, mixture effects were not significantly different from controls, even though significant treatment effects were present for some of the individual compounds. 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, but the reduction in DC activity for the mixture-treated animals was not as great as that in the chloroform-treated group. The significant changes in intestinal microbial metabolism suggest that metabolism or bioactivation of chemical cocontaminants may be altered following exposure to the DBPs chloroform, MX, potassium bromate, or BDCM individually or as a mixture. The effect of the DBP mixture was less than additive.