Transport of anti-glycoprotein IIb/IIIa-antibodies into the alpha-granules of unstimulated human blood platelets.
The redistribution of the antibody-glycoprotein (GP) IIb/IIIa complex was investigated with the immuno-gold labeling technique in order to trace its transport in resting platelets. Washed platelets were incubated in the presence of aspirin and a prostacyclin analogue (iloprost) with three different monoclonal antibodies (Gi3, J15 and P2) against GPIIb/IIIa. The examination of ultrathin serial sections showed that the surface labeling was internalized into the surface connected membrane system (SCS). Labels were found within the alpha-granules after 40 min and the number of labels increased during longer incubation periods (max. 120 min). The transport possibly involved coated membranes. The alpha-granules were neither found to be altered during this process nor were any morphological signs of platelet activation detectable. The anti-GPIIb/IIIa complex remained membrane-associated during the transfer. These observations indicate that the membrane-GPIIb/IIIa complex was stable and transported from the surface into the alpha-granules of resting platelets. Since this transport was not influenced by iloprost or by aspirin it may be interpreted as constitutive endocytosis.
Morgenstern
E
E
Medizinische Biologie, Universität des Saarlandes, Homburg/Saar, Federal Republic of Germany.
Ruf
A
A
Patscheke
H
H
D000911:Antibodies, Monoclonal / Q000097:blood*; D001693:Biological Transport, Active; D001792:Blood Platelets / Q000276:immunology* / Q000378:metabolism / Q000648:ultrastructure; D003594:Cytoplasmic Granules / Q000276:immunology / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D016253:Microscopy, Immunoelectron; D010980:Platelet Membrane Glycoproteins / Q000276:immunology* / Q000378:metabolism
D000911:Antibodies, Monoclonal; D010980:Platelet Membrane Glycoproteins