Effects of beta2-glycoprotein-I on platelet aggregation in cord versus adult whole blood.
We present a peculiarity of the neonatal hemostatic system that might contribute to establish a procoagulant readiness in neonatal blood by sensitizing neonatal platelets for ADP stimulation. beta2-glycoprotein-I (beta2-GP-I) is a plasma constituent capable of suppressing ADP-induced platelet aggregation. We found significant lower levels of beta2-GP-I in cord vs. adult plasma (120 +/- 27 vs. 180 +/- 37 microg/mL, P<0.001). We demonstrate dose-dependent inhibition of ADP-induced platelet aggregation in cord whole blood (WB) in the presence of increasing amounts of beta2-GP-I, evaluated by means of WB aggregometry employing the impedance method. Particularly, raising the beta2-GP-I concentration in cord WB from neonatal level up to the respective adult value caused significant reduction of amplitude (from 9.5 +/- 2.7 to 2.8 +/- 0.9 Omega, P<0.001) and of slope (from 5.9 +/- 2.4 to 1.89 +/- 0.9 Omega/min, P<0.001), and a significant prolongation of the aggregation time (from 51.8 +/- 22.9 to 110.8 +/- 60.3 s, P<0.001). In conclusion, physiological low levels of beta2-GP-I in cord WB cause enhanced responsiveness of neonatal platelets to ADP stimulation. This mechanism might help to explain the clinically observed well-functioning hemostasis in neonates.
Cvirn
Gerhard
G
Institute of Physiological Chemistry, Medical University of Graz, Graz, Austria. gerhard.cvirn@meduni-graz.at
Gallistl
Siegfried
S
Koestenberger
Martin
M
Kutschera
Joerg
J
Ferstl
Ulrika
U
Kellner
Josef
J
Jurgens
Gunther
G
Gries
Anna
A
D000244:Adenosine Diphosphate / Q000494:pharmacology; D000328:Adult; D000367:Age Factors; D005260:Female; D005312:Fetal Blood / Q000502:physiology*; D006487:Hemostasis; D006801:Humans; D007231:Infant, Newborn / Q000097:blood*; D008297:Male; D010974:Platelet Aggregation / Q000187:drug effects; D053482:beta 2-Glycoprotein I / Q000032:analysis / Q000494:pharmacology* / Q000502:physiology
D053482:beta 2-Glycoprotein I; D000244:Adenosine Diphosphate