Linked Life Data

7910786

Source:http://linkedlifedata.com/resource/pubmed/id/7910786

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
2
pubmed:dateCreated
1994-6-29
pubmed:abstractText
The ability of the multidrug resistance modifiers R- and R,S-verapamil (VPL), cyclosporine A (CsA) and its non-immunosuppressive derivative SDZ PSC 833 (PSC 833) to inhibit P-glycoprotein (P-gp)-mediated transepithelial flux of tritiated vinblastine was investigated using tight and highly resistant (R > 1,400 omega cm2) monolayer cultures of intestinal adenocarcinoma-derived HCT-8 cells grown on permeable tissue-culture inserts. Apical addition of these chemosensitizers inhibited drug flux (137 pmol h-1 cm-2; range, 133-142 pmol h-1 cm-2) in the basal to apical secretory direction at clinically relevant concentrations, with PSC 833 showing the highest activity, exhibiting inhibition at concentrations as low as 10 ng/ml (9 nM). Acidification of the modulator-containing apical compartment to an extracellular pH (pHo) of 6.8 had no influence on MDR reversal by CsA at 1 microgram/ml (0.9 microM; flux inhibition, 52%) or by PSC 833 at 100 ng/ml (0.09 microM; flux inhibition, 60%), in contrast to R,S- and R-VPL, which showed decreased inhibition and caused less accumulation of vinblastine in HCT-8 cells under this condition (flux inhibition of 35% and 23%, respectively, at pHo 6.8 vs 50% and 43%, respectively, at pHo 7.5). P-gp-mediated rhodamine 123 efflux from dye-loaded single-cell suspensions of HCT-8 cells as measured by flow cytometry was not impeded at pHo 6.8 in comparison with pHo 7.5 in standard medium, but at low pHo the inhibitory activity of R-VPL (29% vs 60% rhodamine 123 efflux inhibition) was diminished significantly, again without a reduction in the effect of PSC 833 (rhodamine 123 flux inhibition, 75%). In conclusion, drug extrusion across polarised monolayers, which offer a relevant model for normal epithelia and tumour border areas, is inhibited by the apical presence of R,S- and R-VPL, CsA and PSC 833 at similar concentrations described for single-cell suspensions, resulting in increased (2.2- to 3.7-fold) intracellular drug accumulation. Functional apical P-gp expression, the absence of paracellular leakage and modulator-sensitive rhodamine 123 efflux in single HCT-8 cells indicate a P-gp-mediated transcellular efflux in HCT-8 monolayers. In addition to its high MDR-reversing capacity, the inhibitory activity of PSC 833 is not affected by acidic extracellular conditions, which reduce the VPL-induced drug retention significantly. As far as MDR contributes to the overall cellular drug resistance of solid tumours with hypoxic and acidic microenvironments, PSC 833 holds the greatest promise for clinical reversal of unresponsiveness to the respective group of chemotherapeutics.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:issn
0344-5704
pubmed:author
pubmed:issnType
Print
pubmed:volume
34
pubmed:owner
NLM
pubmed:authorsComplete
N
pubmed:pagination
125-32
pubmed:dateRevised
2006-11-15
pubmed:meshHeading
pubmed-meshheading:7910786-Adenocarcinoma, pubmed-meshheading:7910786-Antineoplastic Combined Chemotherapy Protocols, pubmed-meshheading:7910786-Biological Transport, pubmed-meshheading:7910786-Carrier Proteins, pubmed-meshheading:7910786-Cyclosporine, pubmed-meshheading:7910786-Cyclosporins, pubmed-meshheading:7910786-Depression, Chemical, pubmed-meshheading:7910786-Drug Resistance, pubmed-meshheading:7910786-Drug Screening Assays, Antitumor, pubmed-meshheading:7910786-Humans, pubmed-meshheading:7910786-Hydrogen-Ion Concentration, pubmed-meshheading:7910786-Ileal Neoplasms, pubmed-meshheading:7910786-Ileocecal Valve, pubmed-meshheading:7910786-Membrane Glycoproteins, pubmed-meshheading:7910786-Neoplasm Proteins, pubmed-meshheading:7910786-P-Glycoprotein, pubmed-meshheading:7910786-Tumor Cells, Cultured, pubmed-meshheading:7910786-Verapamil, pubmed-meshheading:7910786-Vinblastine
pubmed:year
1994
pubmed:articleTitle
Inhibition of P-glycoprotein-mediated vinblastine transport across HCT-8 intestinal carcinoma monolayers by verapamil, cyclosporine A and SDZ PSC 833 in dependence on extracellular pH.
pubmed:affiliation
I. Department of Surgery, University of Vienna, Austria.
pubmed:publicationType
Journal Article, Comparative Study, Research Support, Non-U.S. Gov't