Possibly the easiest assay for P glycoprotein-mediated MDR uses calcein
AM, which is selectively excreted by MDR cells rather than an antibody.
http://www.probes.com/handbook/sections/1505.html
Biochim Biophys Acta 1994 May 11;1191(2):384-8
Calcein accumulation as a fluorometric functional
assay of the multidrug transporter.
Hollo Z, Homolya L, Davis CW, Sarkadi B.
National Institute of Haematology, Blood
Transfusion and Immunology, Budapest, Hungary.
Acetoxymethyl ester (AM) derivatives of various
fluorescent indicators (fura-2, fluo-3, indo-1, BCECF, calcein) are
actively extruded
by the multidrug transporter (MDR1,
P-glycoprotein-Homolya, L. et al. (1993) J. Biol. Chem. 268,
21493-21496). In the present
paper we show that the measurement of the
accumulation of a fluorescent cell viability marker, calcein, can be
effectively used as a
rapid and sensitive fluorometric and flow
cytometric assay for studying P-glycoprotein function. The rate of
calcein accumulation in
human MDR1-expressing cells is significantly
lower than in the control cells, while various drug-resistance reversing
agents (verapamil,
vinblastine, oligomycin, cyclosporin A and UIC2
monoclonal antibody) greatly increase calcein trapping only in the
MDR1-expressing
cells. Since calcein-AM is not fluorescent and
free calcein is not a substrate of the multidrug transporter, the assay
is readily applicable
for rapid kinetic studies of the MDR1 function.
Calcein has a high fluorescence intensity in the visible range, thus
changes in calcein
uptake can be easily visualised and
MDR1-expressing and control cells separated by conventional flow
cytometry.
Karatza wrote:
> Dear all,Does anybody has any experience in mdr and flow ? What are
> the best antibodies?
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