This study shows that flow cytometry analysis of the rate of fluorochrome Rh123 efflux may be used for detection of cells at initial steps of P-glycoprotein expression and of minor subpopulations of multidrug-resistant (MDR) variants in human cell lines. This method also evaluates the fraction of low-level MDR cells among peripheral blood leukocytes of patients with chronic myeloid leukemia. The alterations in Pgp function were revealed in rat hepatoma cells after short treatment with colchicine.
