You are here:
DIBROMONITROMETHANE-INDUCED INHIBITION OF CELL PROLIFERATION AND FORMATION OF DNA ADDUCTS IN THE LIVER OF MALE AND FEMALE F344 RATS
Citation:
KLIGERMAN, A. D., A. KHAMDY, D. SEED, H. ABU-ZAYED, L. C. KING, M. H. GEORGE, AND A. B. DEANGELO. DIBROMONITROMETHANE-INDUCED INHIBITION OF CELL PROLIFERATION AND FORMATION OF DNA ADDUCTS IN THE LIVER OF MALE AND FEMALE F344 RATS. Presented at Environmental Mutagen Society Meeting, Vancouver, BC, CANADA, September 16 - 20, 2006.
Description:
The halonitromethanes comprise a class of disinfection by-products (DBPs) that were classified as high priority DBPs for health effects research by the U.S. EPA. Although in vitro studies have found that halonitromethanes are potent mammalian cell cytotoxins and genotoxins, no in vivo toxicity studies were available. For this study male and female F344/N rats were exposed to 0, 0.05, 0.5, 5.0, and 50 mg/L dibromonitromethane (DBNM) in the drinking water for 30 days. Two h prior to necropsy, each rat was injected ip with 100 mg/kg bromodeoxyuridine (BrdU). Representative sections of livers and kidneys were removed and fixed in 10% buffered formalin for 24 h and then transferred to 70% ethanol. The tissues were processed into paraffin blocks, sectioned onto glass slides, and stained with H & E or for BrdU incorporation using immunohistochemical techniques. Blocks of fresh liver were frozen for the measurement of DNA-DBNM adducts. No compound-induced morphologic effects were observed during light microscopic examination of the liver, kidney or other selected organs. DBNM-DNA adducts were found in the livers of both male and female rats. DBNM was also found to react directly with calf thymus DNA, 2'-deoxyguanosine-3-monophosphate, and 2'-deoxyadenosine-3-monophosphate suggesting that it is a direct-acting DNA- damaging agent. Digital images from sections of kidney and liver were made using a brightfield microscope equipped with a digital camera interfaced with a PC to quantitate the percentage of BrdU-labeled cells. Ten images per slide were recorded so that approximately 2000 cells were scored per sample. A macro program was developed for the software imaging program, Image J to count the total number of cells. The number of BrdU-labeled cells was counted manually. The analyses indicated that DBNM had no effect on cell turnover in the kidney of the female rats, but caused a marginal dose- dependent decrease in labeling in male kidney cells. In contrast, DBNM caused a dose- dependent decrease in labeling in the hepatocytes of both sexes at all doses examined. These results demonstrate DBNM-induced biochemical and proliferative changes in the absence of gross morphologic effects.