Membrane Fluidity and Shape of Human Red Blood Cells are Altered by PhysiologicalLevels of Hydrostatic Pressure

摘要

The effect of hydrostatic pressure at physiological levels, such as that appliedto humans in diving or hyperbaric chamber, on human red blood cell (RBC) membrane fluidity and morphology was studied. Membrane fluidity was determined by fluorescence anisotropy (FA) of lipid probes (mainly diphenyl hexatriene (DPH), and of tryptophan), as well as by energy transfer from the tryptophan to the lipid probes, in ghosts prepared prior to or after application of pressure to intact RBC. The morphology of intact RBC, prior to or after application of pressure, was evaluated by scanning electron microscopy. It was found that (1) The FA of DPll, which resides in different apolar membrane regions, was increased as a function of the pressure applied and the duration of the treatment. At 15 atm the FA increased by 50%, reaching a plateau after 60 min of application of pressure. (2) Increased FA, to various extents, was observed also with the lipid probes which reside in the membrane lipid core, but not with probes which monitor the polar/apolar phospholipid interface, or the cell surface. (3) The same treatment increased tryptophan anisotropy by about 20%. (4) Tryptophan energy transfer to the lipid probes which resides in the lipid core was increased to various degrees which were related to the increase of the FA of these probes. (5) Following application of 15 atm for 1 hour, at least 60% of the RBC change their shape from discocytes to stomatocytes. These results demonstrate that hydrostatic pressure at physiological levels, might induce reduction of the membrane fluidity of RBC, which affects the physical state of protein environment, and might alter RBC morphology.