Inhibition of P-glycoprotein-mediated transport by a hydrophobic contaminant in commercial gluconate salts

Carlos G. Vanoye, Guillermo A. Altenberg, Luis Reuss*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

1 Scopus citations


The substitution of gluconate for Cl- is commonly used to characterize Cl- transport or Cl--dependent transport mechanisms. We evaluated the effects of substituting gluconate for Cl- on the transport of the P- glycoprotein substrate rhodamine 123 (R123). The replacement of Ringer solution containing Cl- (Cl-Ringer) with gluconate-Ringer inhibited R123 efflux, whereas the replacement of Cl- by other anions (sulfate or cyclamate) had no effect. The inhibition of R123 efflux by gluconate-Ringer was absent after chloroform extraction of the sodium gluconate salt. The readdition of the sodium gluconate-chloroform extract to the extracted gluconate-Ringer or to cyclamate-Ringer inhibited R123 efflux, whereas its addition to Cl--Ringer had no effect. These observations indicate that the inhibition of P-glycoprotein-mediated R123 transport by gluconate is due to one or more chloroform-soluble contaminants and that the inhibition is absent in the presence of Cl-. The results are consistent with the fact that P- glycoprotein substrates are hydrophobic. Care should be taken when replacing ions to evaluate membrane transport mechanisms because highly pure commercial preparations may still contain potent contaminants that affect transport.

Original languageEnglish (US)
Pages (from-to)C1439-C1442
JournalAmerican Journal of Physiology - Cell Physiology
Issue number6 45-6
StatePublished - Jul 21 1999


  • Chloride
  • Ion substitution
  • Multidrug resistance
  • Rhodamine 123
  • Transport

ASJC Scopus subject areas

  • Physiology
  • Cell Biology

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