Transmembrane redistribution of phospholipids of the human red cell membrane during hypotonic hemolysis.
The transmembrane distribution of spin-labeled phospholipids was measured in human erythrocytes before and after hypotonic hemolysis by electron paramagnetic resonance. With a first series of partially water soluble probes a complete randomization of phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine and sphingomyelin analogues was achieved when cells were resealed in the absence of Mg-ATP or when the aminophospholipid translocase was inhibited by vanadate or calcium. If the ghosts were resealed with Mg-ATP inside, the transmembrane asymmetry of the aminophospholipids was reestablished. With long chain insoluble spin-labeled lipids complete randomization was obtained with the phosphatidylcholine analogue but even in the presence of vanadate only a small percentage (approx. 15%) of the spin-labeled phosphatidylserine flopped to the outer monolayer and comparable percentage of the spin-labeled sphingomyelin flipped to the inner monolayer, indicating a hierarchy in the phospholipid redistribution for these water insoluble lipids during hemolysis. The mechanism by which a selective randomization takes place is not known. It may involve phosphatidylserine-protein interactions in the inner leaflet and sphingomyelin-cholesterol or sphingomyelin-sphingomyelin interaction in the outer leaflet.
Schrier
S L
SL
Division of Hematology, Stanford University School of Medicine, CA.
Zachowski
A
A
Hervé
P
P
Kader
J C
JC
Devaux
P F
PF
D004578:Electron Spin Resonance Spectroscopy; D004910:Erythrocyte Membrane / Q000378:metabolism*; D006461:Hemolysis; D006801:Humans; D007700:Kinetics; D010084:Oxidation-Reduction; D010743:Phospholipids / Q000378:metabolism*
D010743:Phospholipids