Characterization of phosphine complexes of technetium(III) as transport substrates of the multidrug resistance P-glycoprotein and functional markers of P-glycoprotein at the blood-brain barrier

Biochemistry. 1997 Nov 18;36(46):14218-27. doi: 10.1021/bi971931z.


The multidrug resistance (MDR1) P-glycoprotein functions as a broad specificity efflux transporter of structurally diverse natural product and xenobiotic compounds. P-glycoprotein also is an important component of the functional blood-brain barrier. To enable further studies of function and modulation of MDR1 P-glycoprotein in vitro and in vivo, two novel phosphine technetium(III) complexes were designed and characterized: trans-[2,2'-(1, 2-ethanediyldiimino)bis(1, 5-methoxy-5-methyl-4-oxo-hexenyl)]bis[methylbis(3-methoxy-1- propyl)ph osphine]Tc(III) (Tc-Q58) and trans-[5,5'-(1,2-ethanediyl diimino)bis(2-ethoxy-2-methyl-3-oxo-4-pentenyl)]bis[dimethyl(3- methox y-1-propyl)phosphine)]Tc(III) (Tc-Q63). In human drug-sensitive KB 3-1 cells and multidrug-resistant KB 8-5 and 8-5-11 derivative cell lines, expressing nonimmunodetectable, low, and high levels of MDR1 P-glycoprotein, respectively, accumulation of Tc-Q58 and Tc-Q63 was inverse to expression of the transporter. Differences between drug-sensitive and multidrug-resistant cells, while detectable at picomolar concentrations of each radiopharmaceutical, were independent of tracer concentration. Ratios of tracer accumulation in KB 3-1 and 8-5 cells were 62.3 and 48.1 for Tc-Q58 and Tc-Q63, respectively. Cell contents of Tc-Q58 and Tc-Q63 were enhanced up to 60-fold in MDR cells by known modulators of MDR1 P-glycoprotein, while drugs not in the multidrug-resistant phenotype had no effect on their accumulation. In KB 8-5 cells, potency of modulators was GF120918 >> cyclosporin A > verapamil. Accumulation of Tc-Q58 and Tc-Q63 in Sf9 insect cells infected with a recombinant baculovirus containing human MDR1 P-glycoprotein was reduced in a GF120918-reversible manner (EC50 </= 70 nM) compared with cells infected with a wild-type baculovirus. By contrast, cell contents of Tc-Q58 or Tc-Q63 in Sf9 cells expressing the homologous MDR3 P-glycoprotein did not differ from wild-type virus. Demonstrating molecular targeting of these complexes in vivo, distribution and retention of Tc-Q58 in brain tissue of FVB mice treated with a saturating dose of GF120918 and mice deficient in the mdr1a gene [mdr1a (-/-)] were enhanced 180% and 520% over control, respectively. Exploiting the gamma-emission spectrum of 99mTc, increased uptake of Tc-Q58 in brain tissue of mdr1a (-/-) mice was readily detected noninvasively by scintigraphic imaging. Thus, both Tc-Q58 and Tc-Q63 are demonstrated to be substrates for transport by MDR1 P-glycoprotein, broadening the specificity of this transporter to include phosphine-containing metal complexes. As shown with Tc-Q58, these Q complexes can be used to detect transport activity and modulation of MDR1 P-glycoprotein in vitro and to directly monitor the functional status of P-glycoprotein at the blood-brain barrier in vivo.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • ATP Binding Cassette Transporter, Subfamily B*
  • ATP Binding Cassette Transporter, Subfamily B, Member 1 / drug effects
  • ATP Binding Cassette Transporter, Subfamily B, Member 1 / genetics
  • ATP Binding Cassette Transporter, Subfamily B, Member 1 / metabolism*
  • ATP-Binding Cassette Transporters / drug effects
  • ATP-Binding Cassette Transporters / genetics
  • ATP-Binding Cassette Transporters / metabolism*
  • Acridines / pharmacology
  • Animals
  • Biological Transport
  • Blood-Brain Barrier / physiology*
  • Brain / diagnostic imaging
  • Isoquinolines / pharmacology
  • Mice
  • Mice, Mutant Strains
  • Molecular Probes*
  • Organophosphorus Compounds / metabolism*
  • Organotechnetium Compounds / metabolism*
  • Radionuclide Imaging / methods
  • Recombinant Proteins / metabolism
  • Tetrahydroisoquinolines*
  • Tumor Cells, Cultured


  • (2,2'-(1,2-ethanediyldimino)bis(1,5-dimethoxy-5-methyl-4-oxohexenyl))bis(methylbis(3-methoxy-1-propyl)phosphine)technetium(III)
  • (5,5'-(1,2-ethanediyldimino)bis(2-ethoxy-2-methyl-3-oxo-4-pentenyl)bis(dimethyl(3-methoxy-1-propyl)phosphine))technetium(III)
  • ATP Binding Cassette Transporter, Subfamily B
  • ATP Binding Cassette Transporter, Subfamily B, Member 1
  • ATP-Binding Cassette Transporters
  • Acridines
  • Isoquinolines
  • Molecular Probes
  • Organophosphorus Compounds
  • Organotechnetium Compounds
  • Recombinant Proteins
  • Tetrahydroisoquinolines
  • multidrug resistance protein 3
  • Elacridar