Purpose: The purpose of this study was to determine the transport and metabolism of dietary carcinogen, 2-Amino-1-methyl-6-phenylimidazo(4,5-b)pyridine (PhIP) in Caco-2 cells and four-site single-pass rat intestinal perfusion model.
Methods: Male Sprague-Dawley (SD) and Fisher (F344) rats (70-110 days old) weighing between 260 and 350 g, were perfused with 100 µM PhIP at a flow rate of 0.382 ml/min for 2.5 hours and intestinal perfusates and bile samples were collected. Apical to basolateral and basolateral to apical transport of 100 µM PhIP was measured in 21 days old Caco-2 TC7 cells in HBSS buffer (pH7.4) at 37°C
Results: The Permeability (P*eff) of 100µM PhIP in rat intestine at four sites (duodenum, jejunum, Ileum and colon) were comparable in SD and F344 rats (Fig. 1). However, colon of SD rats showed slightly lower absorption than colon of F344 rats. Several metabolites of PhIP were detected in bile samples, but no metabolites were detected in perfusate samples. 100 µM PhIP was moderately transported from both apical to basolateral side (P = 1.59 ± 0.07 x 10-6 cm/sec) and basolateral to apical side (P = 2.32 ± 0.09 x 10-6 cm/sec) in Caco-2 cells. No significant amount of PhIP metabolites were detected in the Caco-2 cells transport study, confirming data from perfusion study that intestine is not the important site of metabolism for PhIP.
Conclusion: In conclusion, PhIP was moderately absorbed but very poorly metabolized throughout the length of rat intestine and in Caco-2 cells. Several metabolites of PhIP were detected in bile samples indicating liver to be the primary site of metabolism of PhIP in rats.