UPTAKE AND SUBCELLULAR-LOCALIZATION OF DAUNORUBICIN AND ADRIAMYCIN IN CULTURED FIBROBLASTS

Cellular uptake and subcellular localization of daunorubicin and adriamycin were studied in cultured rat embryo fibroblasts. Both drugs accumulated in the cells manifold above the extracellular concentration. The uptake of daunorubicin was 2-3 time higher than that of adriamycin. Cell fractionation techniques, including isopycnic centrifugation of cytoplasmic extracts, revealed that both drugs were exclusively localized in nuclei and lysosomes, but to quite different proportions. About 20% of accumulated daunorubicin was localized in the nuclei, as compared to 60% of adriamycin, which means that the nuclear concentrations of the drugs were very similar. In the lysosomes, on the other hand, the accumulation of daunorubicin was 4-5 times higher than that of adriamycin. The reason for this difference is so far not clear. The results give an explanation for observations of similar biologic effects of the drugs in spite of a marked difference in cellular accumulation. © 1978.