EFFECT OF CELLULAR INTERACTIONS OF THE P- GLYCOPROTEIN-MEDIATED MULTIDRUG-RESISTANCE

The role of cellular interaction in the resistance of Djungurlan hamst er cells to colchicine (CH) and in the efficiency of Pgp functioning w as studied. Mixtures of CH-resistant acid CH-sensitive cells as well a s control unmixed cells were propagated for 3 days, and their sensitiv ity to CH was measured by the colony forming assay. Individual subpopu lations were identified using a genetic marker (6TG-resistance). The s urvival of the CH-sensitive cells in a CH-supplemented medium increase d after co-cultivation with the CH-resistant counterparts. The activit y of Pgp was measured using fluorescent dye RH123 and the FACScan anal ysis. The Pgp-mediated RH123 efflux increased after co-cultivation of the CH-sensitive and CH-resistant cells. Cellular contact were not nec essary for enhancing the CH-resistance of the cells: cells displayed a n increased drug resistance both in dense and sparse monolayers alter co-cultivation with their drug-resistant variants; the effect persiste d when the resistant and sensitive cells were separated by a partition . The medium conditioned by the resistant cells communicated the CH-re sistance to the drug sensitive cells.