Abstracts
1998 Digestive Disease Week

963

BILE SALT-INDUCED MUTATION IN VITRO. J. Theisen, J.H. Peters, M. Hughes, N. Baril, K. Skinner, C.G. Bremner, G.M.R. Campos,
O.L. Gastal, M. Hashemi, D. Nhera, T.R. DeMeester, P.W. Laird Department of Surgery, University of Southern California, Los Angeles, California.

Background: Considerable clinical and experimental evidence suggests that duodenal juice contributes to the development of Barrett's esophagus and subsequently to adenocarcinoma. Bile salts are among the most likely toxic components. Few studies have directly examined the genetic effects of bile salts, particularly in an environment of pH<7. The aim of this study was to assess the mutagenicity of bile salt exposure at various pH values in vitro. Method: Fibroblasts from Fisher 144 rats in which the LacI gene had been inserted (Big Blue, Stratagene Inc) were exposed 2 hours daily for 75 days to 500µmol glycodeoxycholic acid at pH5 and pH7. Following bile salt exposure the DNA was extracted with phenol-chloroform and the transgene extracted via a phage retrieval system (Big Blue Mutagenesis System, Stratagene). Mutation frequency was calculated as the number of mutant colonies identified in a lawn of transfected E-coli. Results: A significant increase in mutation frequency was seen in cells exposed to 500µmol glycodeoxycholic acid when compared to control values (33x10-5 vs 19.34x10-5, p=0.03). Mutation frequency was not increased at pH7. Cell growth was only minimally affected indicating that the treatment was not toxic to the cells.

Conclusion: Glycodeoxycholic acid may be mutagenic in vitro at a low pH. Previous reports of the lack of mutagenicity of bile salts may have been biased by pH7 in vitro experimental systems.

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