GENOTOXIC ACTIVITY IN HUMAN FECAL WATER AND THE ROLE OF BILE-ACIDS - A STUDY USING THE ALKALINE COMET ASSAY

Human faecal waters from 35 healthy non-smoking volunteers (23 from En gland and 12 from Sweden) consuming their habitual diet were screened for genotoxicity by the single-cell gel electrophoresis (comet) assay using a human colon adenocarcinoma cell line (CACO-2) as the target, H ydrogen peroxide induced DNA damage was categorized as low, intermedia te or high for tail moments greater than 5, 17 and 32, respectively: 1 1 samples were highly genotoxic, four were intermediate, one was low a nd 19 showed no activity, Endonuclease III treatment significantly inc reased DNA damage for all except the non-genotoxic faecal waters, sugg esting that faecal water genotoxicity may be due, at least in part, to oxidative damage, Faecal water cytotoxicity has previously been attri buted to the bile and fatty acid content, In the comet assay no DNA da mage was induced by deoxycholate or lithocholate at normal physiologic al concentrations, suggesting that the genotoxicity of faecal water wa s due to other substances, Both bile acids induced DNA damage above 30 0 mu M, levels often found in patients with colonic polyps and there w as a significant increase in genotoxicity after endonuclease III treat ment indicative of oxidative DNA damage.