Biochemical properties of platelet microparticle membranes formed during exocytosis resemble organelles more than plasma membrane.
Studies of [3H]glycerol turnover in phosphatidylcholine (PC) in platelets revealed two metabolic pools, a 'low turnover PC' in collagen-induced microparticles with specific radioactivity only 10% of that found in the 'high turnover PC' of bulk platelet PC. Isolated organelle fractions of [3H]glycerol-labelled platelets contained [3H]PC with specific radioactivities about 20% of that in membrane fractions. These results together with studies on distribution of concanavalin A-FITC and GPlb, a plasma membrane receptor, indicate that microparticles formed during exocytosis are not simple vesiculations of plasma membrane, but they seem rather to originate from a relatively metabolically static membrane pool not accessible to extracellular reagents.
Olas
Beata
B
Department of Biochemistry and Molecular Biology, University of Bergen, Arstadveien 19, 5009, Bergen, Norway.
Lundell
Kerstin
K
Holmsen
Holm
H
Fukami
Miriam H
MH
D001792:Blood Platelets / Q000737:chemistry* / Q000378:metabolism; D002462:Cell Membrane / Q000737:chemistry* / Q000378:metabolism; D003208:Concanavalin A / Q000493:pharmacokinetics; D005089:Exocytosis / Q000502:physiology*; D005434:Flow Cytometry; D016650:Fluorescein-5-isothiocyanate / Q000031:analogs & derivatives* / Q000493:pharmacokinetics; D005456:Fluorescent Dyes / Q000493:pharmacokinetics; D005990:Glycerol / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D007770:L-Lactate Dehydrogenase / Q000032:analysis / Q000378:metabolism; D015388:Organelles / Q000737:chemistry* / Q000378:metabolism; D010713:Phosphatidylcholines / Q000737:chemistry / Q000378:metabolism; D019038:Platelet Glycoprotein GPIb-IX Complex / Q000032:analysis / Q000378:metabolism; D013347:Subcellular Fractions / Q000737:chemistry; D014316:Tritium
D005456:Fluorescent Dyes; D010713:Phosphatidylcholines; D019038:Platelet Glycoprotein GPIb-IX Complex; C042784:fluorescein isothiocyanate-concanavalin A; D014316:Tritium; D003208:Concanavalin A; D007770:L-Lactate Dehydrogenase; D016650:Fluorescein-5-isothiocyanate; D005990:Glycerol