Effect of heparin on in vivo platelet factor 4 (PF4) release and platelet aggregation after aspirin administration

Abstract

SurnrnuryWe studied the release in vivo of platelet specific proteins platelet factor 4 (PF4) and /l-thromboglobulin (PTG), and confirmed that only PF4 is released, after heparin intravenous administration. A good correlation was found between platelet count and PF4 and this seems at variance with the idea that the source of released PF4 is vascular endothelium rather than platelets; however, such a possibility cannot be excluded. Although platelet function was blocked by aspirin injection heparin was still able to induce the release of PF4 and exerted a potentiating effect on platelet aggregation induced by ADP and collagen.

The release of β‐ thromboglobulin and platelet factor 4 during extracorporeal circulation for open heart surgery

“…It has been shown recently that when heparin is given intravenously it stimulates a great release of PF4 when measured by radioimmunoassay. Contrary to this the other specific protein (PTG) does not seem to be affected [18,191. The level of PF4 in the sternotomized patients measured 5 min after a 2 mg per kg body weight injection rises only two-fold while BTB remains unchanged.…”

Effects of low-molecular-weight heparin on platelets as compared with commercial heparin

“…We collected samples before and 2.5 and 60min after injection to determine the following tests: Activated partial thromboplastin time (APT-F), anti-factor Xa-speeific assay with a chromogenic peptide substrate S-2222, platelet factor 4 (PF4), B-thromboglobulin (BTG), platelet count and platelet aggregation using adenosine diphosphate (ADP) as aggregating agent in a final concentration of 0.8, 1.0, and 2/xM. The sample collection and the tests were carried out as described before [2,[4][5][6][7][8]. Means, standard errors (SE), and linear correlation analyses were performed using an Olivetti computer Model P6040.…”

“…On the platelet function assayed in vitro, low-molecular-weight (LMW) heparin seems to determine a lesser activation than that produced by high-molecular-weight heparin [3,4]. When heparin is injected in vivo as a bolus, it determines an immediate release of platelet factor 4 (PF4) measured by radioimmunoassay [5]. The aim of our study was to evaluate the pattern on in vivo platelet function and on the clotting systems of a commercial heparin and of a LMW heparin after i.v.…”

Clearance and In Vivo Release by Heparin of Human Platelet Factor 4 (PF4) in the Rabbit

“…When heparin is injected as a bolus, it produces an immediate great increase in the plasma level of PF4 which is subsequently cleared from the circulation (2). This release seems to be dependent on platelet concentration, on heparin dose and prob ably on the condition of the vascular endothelium where this releasable PF4 is supposed to be stored (5,6,7,8).…”