EFFECTS OF INDUCTION OF MULTIDRUG-RESISTANCE ON ACCUMULATION OF TC-99M-SESTAMIBI IN-VITRO

The aim of ow study was to evaluate the speed of induction of drug-res istance and its effects on intracellular MIBI accumulation in establis hed human cell lines in-vitro. Four out of 5 cell lines were sensitive to vincristine, I cell line was vincristine-resistant. All vincristin e sensitive cell lines became vincristine-resistant following drug exp osure. Resistance in low-drug concentrations occured as early as 24 ho urs after exposure and progressed to a roughly 1000-times enhanced res istance within 7 days. induction of drug-resistance was associated wit h significantly decreased MIBI accumulation in 2 cell lines but was un effected in 1 cell line, that was primarily drug sensitive as well as in one cell line that was primarily drug-resistant Our data indicate, that induction of MDR is an extremely rapid process and the developmen t of drug resistance is not always associated with enhanced MIBI extru sion.