diphenylhexatriene and Leukemia-P388

Properties of membranes of intact P388 murine lymphoblastic leukemia and a sub-line selected for resistance to adriamycin (P388/ADR) were examined using two fluorescent probes: diphenylhexatriene (DPH) and trimethylammonium diphenylhexatriene (T-DPH). Time-dependent changes in dye accumulation, fluorescence anisotropy, and lifetimes were measured. Accumulation of DPH, which eventually labels all cellular lipids, increased with time. Uptake of T-DPH, a more membrane-specific probe, reached a maximum in less than 1 min. No alteration could be detected in fluorescence anisotropy or lifetime of either dye associated with anthracycline resistance or anthracycline treatment. The rate of uptake of the T-DPH was not different in P388 versus P388/ADR cell lines, suggesting no differences in membrane "traffic". Calcium-channel antagonists could partially reverse anthracycline resistance in P388/ADR, but this was not accompanied by alterations in fluorescence parameters.

Topics: Animals; Diphenylhexatriene; Doxorubicin; Drug Resistance; Fluorescence Polarization; Fluorescent Dyes; Leukemia P388; Leukemia, Experimental

We have studied the structural order of the lipid phase of plasma membranes from P388 murine leukemia cells and from a Doxorubicin-resistant subline, P388/ADR, using electron spin resonance spectroscopy and fluorescence depolarization measurements. Measurements of the order parameter, S, following incubation of cells from both lines with the N-oxyl-4'-4'-dimethyloxazolidine derivative of 5-ketostearic acid show higher values for the resistant cells at all temperatures where S was measured (4-37 degrees). Fluorescence depolarization measurements following incubation of the cells, or cell fractions, with 1,6-diphenylhexatriene indicate more restricted motion of the probe in resistant cells. These measurements also show increased amounts of cytoplasmic lipid in the resistant cells. The higher degree of structural order in the lipid phase of the plasma membranes of P388/ADR cells and their larger intracellular lipid content may account for the decreased rate of intracellular accumulation of anthracycline drugs (and other compounds) seen in these cells and, in part, for their relative resistance to the cytotoxic effects of these drugs.

Topics: Animals; Cell Membrane; Diphenylhexatriene; Doxorubicin; Electron Spin Resonance Spectroscopy; Leukemia P388; Leukemia, Experimental; Membrane Lipids; Mice; Microscopy, Fluorescence