Absorption of 2-acetylaminofluorene in the guinea-pig colon.

Absorption of the known chemical carcinogen, 2-acetylaminofluorene has been measured in the colon of guinea pigs. Unidirectional influx across the luminal cell membrane was determined in vitro, and transmural absorption across colonic mucosa was evaluated in vivo. The kinetics of unidirectional influx into colon in vitro do not indicate that absorption proceeds by simple diffusion. The observed saturable uptake is indicative of binding of 2-acetylaminofluorene to a cellular component. With 2-acetylaminofluorene present in the lumen in vivo at an initial concentration of 3.5 microM, the rate of absorption decreases over a 20 min period, which also indicates some form of specific interaction between 2-acetylaminofluorene and the intestinal mucosa. We have evaluated the hypothesis that surfactants and a bile salt act as cocarcinogens by increasing the rate of intestinal absorption of 2-acetylaminofluorene. The results lend no support to this possibility.