RT Journal Article
SR Electronic
T1 FUNCTIONAL ASSESSMENT OF MULTIPLE P-GLYCOPROTEIN (P-GP) PROBE SUBSTRATES: INFLUENCE OF CELL LINE AND MODULATOR CONCENTRATION ON P-GP ACTIVITY
JF Drug Metabolism and Disposition
JO Drug Metab Dispos
FD American Society for Pharmacology and Experimental Therapeutics
SP 1679
OP 1687
DO 10.1124/dmd.105.005421
VO 33
IS 11
A1 Taub, Mitchell E.
A1 Podila, Lalitha
A1 Ely, Diane
A1 Almeida, Iliana
YR 2005
UL http://dmd.aspetjournals.org/content/33/11/1679.abstract
AB Compounds known to modulate P-glycoprotein (P-gp) activity were evaluated in cell monolayers expressing P-gp for their effects on the secretory transport of P-gp substrates paclitaxel, vinblastine, and digoxin. Paclitaxel has been proposed to selectively interact with a binding site on P-gp that is distinct from the vinblastine and digoxin-binding site. Using Madin-Darby canine kidney (MDCK)-multidrug resistance-1 (MDR1), MDCK-wild-type (WT), and Caco-2 cell monolayers, the basal-to-apical (BL-AP) apparent permeability (Papp) of [3H]paclitaxel, [3H]vinblastine, and [3H]digoxin in the presence of various concentrations of a series of structurally diverse P-gp substrates and modulators of P-gp function were determined. MDCK-WT cell monolayers demonstrated active secretory transport of all P-gp substrate probes, although the sensitivity to inhibition by verapamil was lower than that demonstrated in MDCK-MDR1 cell monolayers. When evaluated as competitive inhibitors, several known P-gp substrates had no effect or only a slight modulatory effect on the BL-AP Papp of all probe substrates in MDCK-MDR1 cells. The secretory transport of P-gp substrates in MDCK-WT cells was more sensitive to inhibition by known P-gp modulators compared with MDCK-MDR1 cells. Low concentrations of ketoconazole (1–3 μM) activated the BL-AP Papp of [3H]vinblastine and [3H]digoxin in MDCK-MDR1 cells but not in MDCK-WT or Caco-2 cells. Determination of secretory transport in P-gp expressing cell monolayers, such as MDCK-MDR1 and Caco-2, may be complicated by substrate cooperativity and allosteric binding, which may result in the activation of P-gp. In addition, expression of other efflux transporters in these cell lines introduces additional complexity in distinguishing which transporter is responsible for substrate recognition and transport. The American Society for Pharmacology and Experimental Therapeutics