ABSTRACT
A low-density lipoprotein (LDL):daunomycin complex was prepared which contains, on the average, 8 nmol of daunomycin/mg of apolipoprotein. LDL was not perturbed to any significant degree by association with daunomycin, and the complex remained stable at 4 degrees. Fluorescence quenching with DNA and potassium iodide, antibody precipitation, and density flotation studies suggested at least two domains for localization of the daunomycin, the surface region and the hydrophobic core of the LDL particle. Interaction of the LDL:daunomycin complex with P388 leukemic cells which were sensitive or resistant to daunomycin occurred rapidly in both sublines, with quantitatively larger amounts of the drug being cell associated than when free drug was used alone. The cells appeared morphologically intact, with no nuclear damage after short-term incubation with LDL:daunomycin. Subfractionation of cell membranes and organelles from the sensitive and resistant cell lines incubated with LDL:daunomycin showed accumulation of drug in the plasma membrane and microsomal-lysosomal-mitochondrial membranes and an insoluble nuclear chromatin material. Both 125l-labeled apoprotein and daunomycin from a 125l-LDL:daunomycin complex showed enrichment in similar membrane:organelle fractions of the P388 cells.
Subject(s)
Daunorubicin/metabolism , Leukemia P388/metabolism , Leukemia, Experimental/metabolism , Lipoproteins, LDL/metabolism , Animals , DNA, Neoplasm/metabolism , Daunorubicin/therapeutic use , Drug Resistance , Humans , Iodine Radioisotopes , Leukemia P388/drug therapy , Leukemia P388/pathology , Mice , Spectrometry, FluorescenceABSTRACT
The removal of the topmost cell layers of the epidermal stratum corneum by stripping initiates a series of biochemical events which alters the normal homeostatic control of and results in the acceleration of the cell cycle in basal cells which are ten to twenty cell layers removed from the site of stripping. One measure of accelerated events is a stimulation of thymidine incorporation into epidermal DNA at time intervals following stripping. Two peaks of maximal stimulation occur between 12 and 24 hr and 48 and 54 hr after stripping. Stimulation of thymidine incorporation into epidermal DNA by limited stripping is a useful technique for studying the stripping-initiated signal at the stratum corneum and its subsequent translation at the proliferative cell receptor site.
