Clastogenic activity of bile acids and organic acid fractions of human feces.

Chloroform extracts of fecal material from 4 subjects on normal mixed western diets were fractionated to obtain an acid fraction and a hexane extract containing neutrals and bases. The acid fraction from at least 2 of the donors induced an elevated frequency of chromosomal aberrations and exchanges in Chinese hamster ovary (CHO) cells. Since acid steroids are expected to be present in the acid fraction, 5 bile acids were assayed for clastogenic activity in CHO cells. Ursodeoxycholic acid induced chromosomal aberrations and exchanges, and this effect was enhanced by the addition of a microsomal S9 mix. However, the enhancement is probably due to physical factors rather than to enzymatic activity.