Pentachlorophenol alters the molecular organization of membranes in mammalian cells

Abstract

Biophysical measurements of motion parameters for fluorescent and paramagnetic probes partitioned into membranes of mammalian cells have indicated that the lipid bilayers of the membranes become destabilized as a result of treatment with sublethal doses of pentachlorophenol. Decreases in bulk lipid fluidity of up to 50%, which can be attributed to perturbation of the bilayer by the toxicant, were observed for purified plasma membrane and for preparations of total cell membrane. Spin labels that probe the hydrophobic interior and headgroup regions, respectively, of bilayers indicated that pentachlorophenol does not assume an amphipathic orientation in the membrane, but rather it partitions into the hydrophobic interior of the bilayer. Arrhenius plots of motion parameters were continuously linear over temperatures ranging from 20 to 55°C for both treated and control cells, indicating that pentachlorophenol does not induce lipid phase transitions. Treatment with sublethal doses of pentachlorophenol also induced a decline in levels of phospholipid phosphate per cell that can be attributed to a selective action of phospholipase C. Notwithstanding these changes, the cells remained viable judging from their ability to exclude trypan blue and thus the deleterious effects of pentachlorophenol on membranes can be interpreted as sublethal damage.