Mutagenicity of blue rayon extracts of human bile in the Ames test

Geographical variations in the concentration of biliary free fatty acids with anti-mutagenic action

The concentrations and compositions of free fatty acids (FFAs) in human bile, especially of inhibitory free fatty acids (IFFAs), were analyzed in terms of anti-mutagenic effects in relation to the mutagenic activity of bile. Bile samples were collected from patients with cholelithiasis residing in either Niigata or Kochi prefectures of Japan, regions characterized as the highest and lowest risk areas for gallbladder cancer (GBC), respectively. Biliary FFAs and IFFAs were analyzed by high-performance liquid chromatography and mutagenicity was examined in by the Ames test (TA98+S9mix) after blue rayon treatment. There was a tendency for higher biliary FFA and IFFA concentrations in the Kochi subjects, but the proportion of IFFA to the total FFA concentration did not differ between the two areas. There was an inverse correlation between the concentrations of IFFAs and the numbers of revertant colonies in both Niigata and Kochi subjects. However, at a dose of 591 micromol/l, (calculated based on the average amount of IFFAs absorbed in blue rayon) IFFAs did not exhibit anti-mutagenic actions in the blue rayon extracts. Within this range, more positive samples were seen in Niigata than in Kochi, suggesting the presence of more active mutagen(s) in Niigata samples.

Determination of free fatty acids in human bile by high-performance liquid chromatography

We developed a high-performance liquid chromatography (HPLC) method for free fatty acids (FFAs) analysis in bile. In this method, FFAs were extracted from bile in a single step using an Isolute ODS cartridge, derivatized with 9-anthryldiazomethane (ADAM). ADAM was chosen because of its high reactivity with carboxylic acid at room temperature. Then, HPLC was used for separating and quantifying FFAs. This method proved to be simple and time-saving. The mean recovery of FFA added to human gallbladder bile was 97.6%, and the detection limit was 100-250 pg. Using this method, we determined FFA concentrations in the gallbladder bile of 11 gallstone patients. The mean concentration of total FFA was 0.61 (SD = 0.41) mmol/L, and there was wide variation in the individual FFAs.

The use of 32P-postlabelling in studies of the nature and origin of DNA adducts formed by bile from patients with familial adenomatous polyposis and from normal patients

32P-postlabelling is a highly sensitive technique for the detection of DNA adducts. It is unique in that it requires no prior knowledge of the nature of adducts or adduct-forming species under investigation. In the past, we have used this technique to investigate the role of bile in the production of foregut adenomas in patients with familial adenomatous polyposis (FAP). We have found that bile contains constituents that form DNA adducts directly, and after metabolic activation, and that the bile of FAP patients has an increased capacity for adduct formation with DNA in vitro, in human cell lines in culture, and in the gastrointestinal tract of rats given bile by gavage. The sensitivity of 32P-postlabelling is such that it is difficult to obtain sufficient quantities of DNA adducts for chemical analysis. The nature of the adducts produced by bile, or of the bile constituents that produce them is as yet undetermined. In the present studies, we have combined 32P-postlabelling with indirect methods to gain some insight into the nature of DNA adducts produced by bile and the properties of the reactive species that form them. Firstly, bile was incubated with synthetic monodeoxynucleotides or polydeoxynucleotides. Bile did not produce adducts when incubated with monodeoxynucleotides or single-stranded polydeoxynucleotides. However, it did produce adducts when incubated with double-stranded polydeoxynucleotides. The pattern of adduct formation suggested that human bile forms a mixture of adenine and guanine adducts. Secondly, bile was fractionated by extraction with blue cotton or with neutral, acid or alkaline organic solvent. Blue cotton, which efficiently and selectively absorbs mutagens having 3 or more fused aromatic rings, did not absorb biliary constituents that could form adducts with DNA in vitro or with DNA of MCL-5 cells, a metabolically competent human cell line. This suggests that biliary DNA adduct precursors are polar compounds that contain fewer than 3 aromatic rings or are non-aromatic. Acidic organic extracts of human bile produced much higher levels of DNA adducts in vitro or with DNA of MCL-5 cells than did neutral or alkaline organic extracts, suggesting that constituents of bile that form DNA adducts are acidic in nature.

Comparison of mutagenic activity of bile between Chilean and Japanese female patients having cholelithiasis

The mutagenic activity of bile was compared between Chilean and Japanese female patients having cholelithiasis by the Ames assay using Salmonella typhimurium tester strain TA98 in the presence of S9 mix with blue rayon adsorption technique. A reason for conducting the present investigation is that Chile and Japan have the highest mortality rates for the gallbladder cancer (GBC) in the world. Of 24 bile samples collected in Chile, 20 (83.3%) samples showed mutagenicity. In the case of Japanese bile, 21 (80.8%) of 26 and 5 (19.2%) of 26 cases were mutagenic in samples from high- and low-risk areas for GBC, respectively. Therefore, both the Chilean and the Japanese samples collected in high-risk areas showed higher mutagenic rates than the Japanese ones in a low-risk area, with a statistical significance (p < 0.001), chi-square test). The average number of revertant colonies were 128 +/- 92 (mean +/- SD), 62 +/- 14 and 66 +/- 13, respectively, when the blue rayon extracts of 200 microliters bile were applied to the Ames test. Thus, Chilean bile had a tendency to show a higher mutagenic activity than Japanese.

Geographical variations in mutagenicity of blue rayon extracts of Japanese human bile

The mutagenicity of human bile was investigated in the Ames test after blue rayon treatment. In the present study, 52 and 59 bile samples were collected from the high and the low risk population for gallbladder cancer (GBC), respectively. The bile mutagenicity was detected only when the blue rayon extracts of bile were assayed with Salmonella typhimurium TA98 in the presence of S9 mix. Thirty-two (61.5%) of 52 samples obtained from the high risk population were mutagenic. In our previous study (Mano et al., 1993), the mutagenicity was observed in 14 (58.3%) of 24 samples. After combining this data with the results of the present study, 46 (60.5%) of 76 samples revealed the mutagenicity. On the other hand, the mutagenicity was detected in only 7 (11.9%) of 59 samples collected from the low risk population. Therefore, we found a significant geographical difference in the bile mutagenicity.