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THE INDUCTION OF ABERRANT CRYPT FOCI (ACF) IN THE COLONS OF RATS BY TRIHALOMETHANES ADMINISTERED IN THE DRINKING WATER
Citation:
DeAngelo, A B., D. R. Geter, D. W. Rosenberg, AND M H. George. THE INDUCTION OF ABERRANT CRYPT FOCI (ACF) IN THE COLONS OF RATS BY TRIHALOMETHANES ADMINISTERED IN THE DRINKING WATER. CANCER LETTERS 187(1-2):25-31, (2002).
Description:
Bromodichloromethane (BDCM) and bromoform (TBM) had been demonstrated to be colon carcinogens in male and female F344/N rats following administration by corn oil gavage. Our chronic bioassay of BDCM administered in the drinking water failed to demonstrate an enhanced colon cancer in male F344/N rats. The present study addressed the capability of the trihalomethanes (THMs) administered in drinking water to induce aberrant crypt foci (ACF), early putative preneoplastic lesions in the colons of male F344/N rats and the B6C3F1 and A/J mouse strains. Rats and mice were exposed to isomolar concentrations of the THMs [0.5 g/L chloroform (TCM), 0.7 g/L BDCM, 0.9 g/L dibromochloromethane (DBCM), or 1.1 g/L (TBM)] for 10 weeks. BDCM was administered in the drinking water to the A/J mouse for 26 and 30 weeks. Deionized water and 0.25% emulphor were the negative controls; 30 mg/kg azoxymethane (AOM; single ip injection) served as the positive control. No ACF were observed in the colon of mice following 10 weeks (B6C3F1) or 26 and 30 weeks (A/J) of THM treatment. ACF incidence (percent) and number (AFC/colon) in the rat were: combined controls, 0; AOM, 100%, 27.17 ? 6.28 (p < 0.01); TCM,16.7%, 0.17 ? 0.17; BDCM, 83.3%, 1.50 ? 0.56 (p < 0.01); DBCM, 50%, 1.17 ? 0.65 (p < 0.01); TBM, 66.7%, 1.17 ? 0.40 (p < 0.01). THM-induced ACF primarily (92%) occurred in the rectal segment of the colon (segment 3). These studies demonstrate that brominated THMs administered in the drinking water induced preneoplastic ACF in the colon of rats.
Keywords: ACF, colon, trihalomethanes, drinking water,disinfection byproducts