Unexpected results when using MitoTracker Green FM and CCCP treatment in cytometry. How to explain?
We want to evaluate mitochondrial mass. Cells were stained with MitoTracker Green FM (Cat. M7514), whose fluorescence monitors total mitochondrial mass and in particular, we want to study mitochondrial mass at basal conditions and after the treatment with CCCP. Unexpectedly, we found that cells treated with CCCP at different concentrations, had a higher MTG signal.
We have repeated the experiments several times and we always get an increase in the MTG signal.
How can I explain such results?
One possibility is that your cells express a multidrug efflux pump, such as P-gp or MRP, that recognizes MTG-FM as a substrate. Inhibition of the pump by CCCP (either directly or indirectly) allows a higher concentration of MTG-FM into the cells. You can test this concept by replacing CCCP in the experiment with known efflux pump inhibitors that don't affect mitochondrial function, such as cyclosporin A, a fairly potent inhibitor of P-gp and MRP.
Article Cyclosporin A is a broad-spectrum multidrug. resistance modulator
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