Lysosomotropic agents increase vinblastine efflux from mouse MDR proximal kidney cells exhibiting vectorial drug transport.
Vinblastine (VBL) transport and efflux were studied in mouse proximal tubule PKSV-PR cells and in their multidrug-resistant derivatives PKSV-PRcol50 cells. The PKSV-PRcol50 cells produced more mdr1b transcripts and had higher resistance to various drugs. PKSV-PRcol50 cells had a predominantly basal-to-apical flux of [3H]VBL, 2.7 times larger than that in PKSV-PR cells. This flux was partially inhibited by verapamil (VRP) (10 microM) and cyclosporin A (CsA) (200 nM). [3H]VBL efflux was also greater in PKSV-PRcol50 than in PKSV-PR cells. Treatment with NH4Cl (30 mM), a lysosomotropic weak base, and concanamycin A (CCM A) (20 nM), an inhibitor of the vacuolar H+/ATPase, further increased [3H]VBL efflux from PKSV-PRcol50 cells. The cytoplasmic pH (pHcyt) of these drug-resistant cells transiently increased in the presence of NH4Cl deltapHcyt: +0.4). CCM A caused a moderate, delayed increase in pHcyt (deltapHcyt: +0.1) and made the acidic intralysosomal compartment more alkaline (deltapHlys: +1.3). VRP and CsA prevented the NH4Cl- and CCM A-induced [3H]VBL efflux from PKSV-PRcol50 cells. However, VRP (10 microM) did not significantly affect pHcyt of PKSV-PRcol50 cells, the NH4Cl-and CCM A-induced pHcyt responses, and the effect of CCMA on pHlys. Thus, lysosomotropic agents may affect the kinetics of [3H]VBL efflux. Our results also suggest that the inhibitory action of VRP on VBL efflux was not directly mediated by a pH-dependent process in these drug-resistant renal proximal tubule cells.
Lacave
R
R
Laboratoire d'Histologie et Biologie Tumorale, Hôpital Tenon, Paris, France.
Ouar
Z
Z
Paulais
M
M
Bens
M
M
Ricci
S
S
Cluzeaud
F
F
Vandewalle
A
A
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000096:biosynthesis / Q000235:genetics; D000643:Ammonium Chloride / Q000494:pharmacology; D000818:Animals; D001483:Base Sequence; D001693:Biological Transport, Active / Q000187:drug effects; D002460:Cell Line; D016764:Cell Polarity; D003208:Concanavalin A / Q000494:pharmacology; D017931:DNA Primers / Q000235:genetics; D018432:Drug Resistance, Multiple / Q000235:genetics; D004847:Epithelial Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D019450:Genes, MDR; D006863:Hydrogen-Ion Concentration; D007424:Intracellular Fluid / Q000378:metabolism; D007687:Kidney Tubules, Proximal / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D007700:Kinetics; D008247:Lysosomes / Q000187:drug effects; D051379:Mice; D014747:Vinblastine / Q000493:pharmacokinetics*
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D017931:DNA Primers; D000643:Ammonium Chloride; D003208:Concanavalin A; D014747:Vinblastine