HEPARIN REVERSES RHODAMINE-123 EXTRUSION BY MULTIDRUG-RESISTANT CELLS

The effect of heparin as a reversing agent of multidrug resistance (MD R) was tested on normal mononuclear cells from 24 healthy volunteers a nd leukaemic cells from 12 acute myeloid leukaemia, five chronic myelo id leukaemia, five acute lymphoid leukaemia and three chronic lymphoid leukaemia patients. Two cell lines were used as controls, the human e rythroleukaemia K562 and its vincristine-resistant derivative K562-Luc ena 1. Heparin was not cytotoxic by itself as determined using a MTT a ssay and cell counts. MDR modulation was assessed by Rhodamine 123 ext rusion using flow-cytometry. Modulation of the resistant cell line was produced by the classical reversing agent verapamil and also by hepar in, the same being observed in normal and leukaemic cells and being in dependent of the type of leukaemia. Our work suggests that heparin may be considered a potential MDR modulator.