ROLE OF THE MUCOUS SURFACE-COAT, DIETARY BULK AND MUCOSAL CELL TURNOVER IN THE INTESTINAL DISPOSITION OF BENZO(A)PYRENE (BAP)

The dispositon of H-3-benzo(a)pyrene (BaP) equivalents from the diet w as examined at the lumen-mucosal cell interface of the proximal, media l and distal regions of the catfish intestine. H-3-BaP (500 mu Ci, 20 mu g/kg) was administered via gavage in maintenance diet to two groups of catfish. One group was fed daily after dosing while the other was fasted until collection of intestinal tissues. Autoradiography of cryo sectioned tissues and computer-enhanced image analysis allowed examina tion of BaP disposition. BaP was found to selectively localize at high concentrations in the mucous surface coat and corresponding villi of the colon. Supplemental feeding of uncontaminated diet lowered BaP con centrations in these regions. In a similar but separate experiment. H- 3-thymidine (666 mu Ci) was administered to two groups of catfish by i .p. injection to examine mucosal cell turnover in relation to BaP turn over. H-3-Thymidine incorporation was greatest in the distal regions o f both fasted and fed groups. Thymidine dynamics indicated that feedin g was related to only marginal changes in cell turnover, which suggest s that losses in intravillus BaP with feeding may not be wholly explai ned by intestinal cell turnover. Results from this study suggest that the mucous surface coat of the intestine is a major factor in the regi onal disposition of dietary carcinogens and removal of BaP from this m ucin layer is related to the intake of dietary bulk. Copyright (C) 199 6 Elsevier Science Ltd