Rhodamine R123 and the cell cycle
Jacek Witkowski (jawit@amed01.amg.gda.pl)
Mon, 29 May 1995 18:45:59 +0200 (MET DST)
A caveat to all attempting to use Rhodamine R123 as G0/G1 marker in bone
marrow and lymphocytes:
Due to a presence of an universal membrane transporter P-glycoprotein, R123 is
actively eliminated by a subpopulation of human CD34+ hematopoietic
cells (cf. Chaudhary & Roninson, 1991, Cell, 66 : 85) and by some T cells
(in humans: Gupta et al., 1992, J. Clin. Immunol. 12: 451; in mice:
Witkowski & Miller, 1993, J. Imunol. 150: 1296). Our recent observations
(unpublished so far) indicate that also in human cord blood lymphocytes
the level of active R123 exclusion is quite high.
If one wants to use R123 as a mitochondrial marker (which it is!) in
these cells, in hope to see the increase in staining due to G0->G1 shift,
should bear the above in mind and use some kind of blocker of
P-glycoprotein activity (50 uM verapamil will do).
By the way, Hoechst 33342 is also pumped by cells expressing
P-glycoprotein activity (cf. Krishan 1987, Cytometry 8:642; Morgan et al,
1989, Br. J. Cancer 60: 339).
Good luck!
Jacek M. Witkowski MD, PhD
Department of Histology
Flow Cytometry Laboratory
Medical University of Gdansk, Poland
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