title: Outward transfer of dopamine precursor L-3,4-dihydroxyphenylalanine (L-dopa) by native and human P-glycoprotein in LLC-PK(1) and LLC-GA5 col300 renal cells.
abstract: The role of P-glycoprotein (P-gp) in the basal-to-apical uptake and flux of L-3,4-dihydroxyphenylalanine (L-dopa) was studied in LLC-PK(1) and LLC-GA5 Col300 cells, a renal cell line expressing the human P-gp in the apical membrane. In the absence of verapamil, LLC-GA5 Col300 cells accumulate less calcein (0.5 microM) than do LLC-PK(1) cells. In LLC-PK(1) cells, pretreatment with verapamil (25 microM) for 30 min increased the rate of accumulation of calcein by 5-fold, whereas in LLC-GA5 Col300 cells, no significant change in the rate of accumulation of calcein was observed. Exposure for 3 h to verapamil (25 microM) was found to increase the rate of accumulation of calcein by 2.5-fold in LLC-PK(1) cells and by 3. 7-fold in LLC-GA5 Col300 cells. A 30-min exposure to UIC2 (3 microg/ml) or verapamil (25 microM) increased L-dopa accumulation in LLC-PK(1) cells by 27 +/- 4 and 88 +/- 14% and reduced L-dopa apical extrusion by 29 +/- 4 and 23 +/- 1%, respectively. The exposure of LLC-GA5 Col300 cells to UIC2 (3 microg/ml) or verapamil (25 microM) for 30 min produced no significant changes in cell accumulation and apical extrusion of L-dopa. A more prolonged exposure (3 h) to UIC2 or verapamil resulted in a marked increase in L-dopa accumulation in the cell (105 +/- 13 and 146 +/- 24% increase) and a pronounced decrease (91 +/- 1 and 92 +/- 1% reduction) in the apical extrusion of L-dopa. It is concluded that LLC-PK(1) cells are endowed with P-gp and that the outward transfer of L-dopa at the apical cell border in both LLC-PK(1) and LLC-GA5 Col300 cells is in part promoted through this transporter.
authors.affiliation: Institute of Pharmacology and Therapeutics, Faculty of Medicine, Porto, Portugal. Patricio.Soares@mail.telepac.pt
authors.forename: P
authors.initials: P
authors.lastname: Soares-Da-Silva
authors.forename: M P
authors.initials: MP
authors.lastname: Serrão
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000037:antagonists & inhibitors / Q000276:immunology / Q000378:metabolism*; D000818:Animals; D000911:Antibodies, Monoclonal; D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology; D002121:Calcium Channel Blockers / Q000494:pharmacology; D002460:Cell Line; D004298:Dopamine / Q000378:metabolism*; D005452:Fluoresceins / Q000494:pharmacology; D005456:Fluorescent Dyes; D006801:Humans; D007668:Kidney / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D007700:Kinetics; D018374:LLC-PK1 Cells; D007980:Levodopa / Q000378:metabolism*; D011506:Proteins / Q000737:chemistry / Q000378:metabolism; D020112:Rhodamine 123; D013552:Swine; D014700:Verapamil / Q000494:pharmacology; D014747:Vinblastine / Q000494:pharmacology
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000911:Antibodies, Monoclonal; D000972:Antineoplastic Agents, Phytogenic; D002121:Calcium Channel Blockers; D005452:Fluoresceins; D005456:Fluorescent Dyes; D011506:Proteins; D020112:Rhodamine 123; D007980:Levodopa; D014747:Vinblastine; D014700:Verapamil; C007740:fluorexon; D004298:Dopamine