Regulation of the dynamic properties of platelet plasma membrane by intracellular sodium ions.
Our previous experiments in human and rat platelets demonstrated that the absence of extracellular Na+ increased the fluorescence anisotropy of TMA-DPH (trimethylamino-diphenylhexatriene, probe preferentially incorporated into the outer leaflet of the plasma membrane). Here we investigated further the in vitro effects of Na+ ions on membrane dynamic properties. Na(+)-dependent changes were reversible and they required about 10-20 min to be induced. They were specifically located in the TMA-DPH environment because they were not observed with diphenylhexatriene (probe non-selectively incorporated into all hydrophobic domains of the cell). To evaluate the possible influence of the intracellular Na+, the effects of sodium replenishment, monensin, ouabain and thrombin on TMA-DPH anisotropy were measured. A rise in intracellular Na+ above the physiological level was associated with unchanged or slightly decreased TMA-DPH anisotropy whereas its decrease was accompanied by a pronounced rise in TMA-DPH anisotropy. Our data indicate that the changes in intracellular Na+ concentration, rather than those in extracellular Na+ concentration, are responsible for the alterations in platelet membrane fluidity probed by TMA-DPH.
Zicha
J
J
Necker Medical School, CNRS URA 1482, Paris, France.
Kunes
J
J
Le Quan Sang
K H
KH
Devynck
M A
MA
D000818:Animals; D001792:Blood Platelets / Q000187:drug effects / Q000502:physiology* / Q000648:ultrastructure; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D004161:Diphenylhexatriene / Q000031:analogs & derivatives; D005110:Extracellular Space / Q000378:metabolism; D005454:Fluorescence Polarization; D007424:Intracellular Fluid / Q000378:metabolism; D008297:Male; D008536:Meglumine / Q000494:pharmacology; D008560:Membrane Fluidity / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D012964:Sodium / Q000097:blood* / Q000494:pharmacology; D013917:Thrombin / Q000494:pharmacology; D013997:Time Factors
D004161:Diphenylhexatriene; D008536:Meglumine; C033628:1-(4-(trimethylamino)phenyl)-6-phenylhexa-1,3,5-triene; D012964:Sodium; D013917:Thrombin