Rat precision-cut intestinal slices to study P-gp activity and the potency of its inhibitors ex vivo

•P-gp inhibitors can be identified using Precision-Cut Intestinal Slices (PCIS).•Relative potency (IC50) of P-gp inhibitors is correctly predicted in PCIS.•P-gp activity in rat is higher in ileum than in duodenum, jejunum and colon.•P-gp inhibition increases accumulation of Rhodamine 123 in the enterocytes of PCIS.

Rat Precision-Cut Intestinal Slices (PCIS) were evaluated as ex vivo model to study the regional gradient of P-gp activity, and to investigate whether the rank order of inhibitory potency of P-gp inhibitors can be correctly reproduced in this model with more accurate IC50 values than with current in vitro models. PCIS were prepared from small intestine (duodenum, jejunum, ileum) and colon. Rhodamine 123 (R123) was used as P-gp substrate, while verapamil, cyclosporine A, quinidine, ketoconazole, PSC833 and CP100356 were employed as P-gp inhibitors. Increase in tissue accumulation of R123 in the presence of the inhibitors was considered as an indication of the inhibitory effect. The P-gp inhibitors increased the tissue accumulation of R123 in a concentration dependent manner. Fluorescence microscopy elucidated that this increase occurred predominantly in the enterocytes. The rank order of the corresponding IC50 values agreed well with reported values from cell lines expressing rat P-gp. The activity of and inhibitory effects on P-gp were significantly higher in ileum compared to the other regions. These data suggest that rat PCIS are a reliable ex vivo model to study the activity of intestinal P-gp and the inhibitory effect of drugs. PCIS have potential as ex vivo model for the prediction of transporter-mediated drug-drug interactions.