title: Transport characteristics of 9-nitrocamptothecin in the human intestinal cell line Caco-2 and everted gut sacs.
abstract: The intestinal absorptive characteristics and the efflux mechanisms of 9-nitrocamptothecin (9-NC), a novel water-insoluble camptothecin (CPT) derivative, were investigated. The Caco-2 cells and the everted gut sacs were used as models of the intestinal mucosa to assess transepithelial transport of 9-NC. The determination of 9-NC was performed by HPLC. In the Caco-2 cells, the absorptive transport of 9-NC was pH dependent and the transport was enhanced at weakly acidic pH on the apical side. No concentration dependence and saturation were observed for the absorptive transport of 9-NC at concentrations up to 250 microM, while secretory transport were concentration dependent and saturable process (K(m) was 49.8 +/- 1.2 microM, V(max) was 38.28 +/- 0.8 ng/cm(2)/min). In the presence of verapamil (100 microM) and CsA (10 microM), potent inhibitors of P-glyprotein (P-gp)/MRP2 (cMOAT), the P(appBL-AP)/P(appAP-BL) ratio was decreased from 3.4 to 1.4 and 1.3, respectively, and permeation of apical to basolateral was enhanced approximately two-fold. In the everted gut sacs, the absorption of 9-NC was passive diffusion and had no significant difference in different gut regions. Adding verapamil in the everted gut sacs over a concentration ranging from 10 to 100 microM, the absorption of 9-NC was significantly enhanced, especially more markedly in lower small intestine (P < 0.05). Overall, the current study suggests that pH and efflux transporters are capable of mediating the absorption and efflux of 9-NC, and they may play significant roles in limiting the oral absorption of 9-NC.
authors.affiliation: Department of Pharmaceutics, School of Pharmacy, Fudan University, Shanghai 200032, PR China.
authors.forename: Xianyi
authors.initials: X
authors.lastname: Sha
authors.forename: Xiaoling
authors.initials: X
authors.lastname: Fang
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000493:pharmacokinetics*; D001692:Biological Transport; D018938:Caco-2 Cells; D002166:Camptothecin / Q000031:analogs & derivatives* / Q000493:pharmacokinetics*; D016572:Cyclosporine / Q000494:pharmacology; D004386:Duodenum / Q000378:metabolism; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007082:Ileum / Q000378:metabolism; D066298:In Vitro Techniques; D007408:Intestinal Absorption / Q000187:drug effects*; D007413:Intestinal Mucosa / Q000378:metabolism; D007583:Jejunum / Q000378:metabolism; D008297:Male; D008954:Models, Biological; D051381:Rats; D017207:Rats, Sprague-Dawley; D014700:Verapamil / Q000494:pharmacology
chemical_list: D000970:Antineoplastic Agents; D016572:Cyclosporine; D014700:Verapamil; C079905:rubitecan; D002166:Camptothecin