Soluble P-selectin is present in normal circulation and its plasma level is elevated in patients with thrombotic thrombocytopenic purpura and haemolytic uraemic syndrome.
P-selectin is an integral membrane glycoprotein stored in the secretory granules of platelets and endothelial cells. To determine whether soluble P-selectin may be present in the circulation of healthy humans, we used a sandwich immunoassay to assess citrated plasma from 50 subjects. P-selectin was present in concentrations ranging from 19 to 521 ng/ml (mean +/- SD = 121 +/- 84 ng/ml). The apparent molecular weight of P-selectin immunoisolated from platelet-poor plasma was similar to that of the detergent-soluble form isolated from platelet membrane. Plasma levels of P-selectin were unaffected by the following procedures: (1) drawing of blood in the presence of protease inhibitors; (2) stimulation of platelet-rich plasma with aggregating agents; (3) ultracentrifugation at 100,000 g for 120 min at 4 degrees C or filtration through a 0.22 micron membrane; or (4) preincubation of platelet-poor plasma with immobilized anti-platelet glycoprotein Ib monoclonal antibodies. It appeared that plasma P-selectin did not result from the in vitro activation of platelets, nor was it derived from platelet microparticles. We also found that plasma P-selectin levels were significantly elevated in patients with thrombotic thrombocytopenic purpura (12 patients, 332 +/- 184 ng/ml, P < 0.001) and haemolytic uraemic syndrome (17 patients, 297 +/- 191 ng/ml, P < 0.0001), as compared to the normal levels. Thus, these data should facilitate the study of the pathophysiological significance of circulating P-selectin.
Katayama
M
M
Biotechnology Research Laboratories, Takara Shuzo Co. Ltd., Shiga, Japan.
Handa
M
M
Araki
Y
Y
Ambo
H
H
Kawai
Y
Y
Watanabe
K
K
Ikeda
Y
Y
D000328:Adult; D015703:Antigens, CD / Q000032:analysis; D001792:Blood Platelets / Q000737:chemistry; D001800:Blood Specimen Collection / Q000379:methods; D005260:Female; D006463:Hemolytic-Uremic Syndrome / Q000097:blood*; D006801:Humans; D007124:Immunoenzyme Techniques; D008297:Male; D008875:Middle Aged; D008970:Molecular Weight; D019007:P-Selectin; D010974:Platelet Aggregation / Q000502:physiology; D010980:Platelet Membrane Glycoproteins / Q000032:analysis* / Q000737:chemistry; D011697:Purpura, Thrombotic Thrombocytopenic / Q000097:blood*; D012995:Solubility
D015703:Antigens, CD; D019007:P-Selectin; D010980:Platelet Membrane Glycoproteins