title: In vitro transepithelial drug transport by on-line measurement: cellular control of paracellular and transcellular transport.
abstract: Studies on transcellular transport across epithelial cell layers are performed mostly by discontinuous sampling of the transported compound. This has several drawbacks, e.g., it gives disturbances in volume, it limits the time-resolution, and is often laborious. In this report we introduce a method to measure transepithelial transport of fluorescent compounds continuously. The time-resolution is at the (sub)minute scale, allowing the measurement of the change in transport rate before and after transport modulation. We will describe how we used the method to measure transcellular and paracellular transport. For highly membrane-impermeable compounds, the paracellular transport and the regulation of the tight junctions was studied in wild-type and MDR1 cDNA transfected epithelial canine kidney cells (MDCKII). The effect of the multidrug transporter P-glycoprotein (Pgp) on the transepithelial transport was studied. Addition of the Pgp inhibitor SDZ PSC 833 showed a modulation of the idarubicin (IDA) and daunorubicin (DNR) transport, which was larger during transport from the basolateral to the apical side than in the reverse direction. By modeling the transepithelial transport, we found that in these cells Pgp had more effect on the basolateral to apical transport than vice versa, which can be attributed to a relatively large passive permeation coefficient for the cellular basolateral plasma membrane.
authors.affiliation: Academisch Ziekenhuis Vrije Universiteit, Department of Medical Oncology, P.O. Box 7057, Room BR232, 1007 MB Amsterdam, The Netherlands.
authors.forename: P R
authors.initials: PR
authors.lastname: Wielinga
authors.forename: E
authors.initials: E
authors.lastname: de Waal
authors.forename: H V
authors.initials: HV
authors.lastname: Westerhoff
authors.forename: J
authors.initials: J
authors.lastname: Lankelma
mesh_terms: D000465:Algorithms; D000818:Animals; D001693:Biological Transport, Active; D002417:Cattle; D002460:Cell Line; D002478:Cells, Cultured; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D003524:Cyclosporins / Q000737:chemistry; D003630:Daunorubicin / Q000737:chemistry / Q000493:pharmacokinetics; D003911:Dextrans; D004285:Dogs; D004847:Epithelial Cells / Q000378:metabolism*; D016650:Fluorescein-5-isothiocyanate / Q000031:analogs & derivatives; D019450:Genes, MDR / Q000235:genetics; D006801:Humans; D015255:Idarubicin / Q000737:chemistry / Q000493:pharmacokinetics; D008954:Models, Biological; D009862:Online Systems; D019108:Tight Junctions / Q000378:metabolism
chemical_list: D003524:Cyclosporins; D003911:Dextrans; C015219:fluorescein isothiocyanate dextran; D016650:Fluorescein-5-isothiocyanate; C070272:valspodar; D015255:Idarubicin; D003630:Daunorubicin