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>Combined activation of platelets by cathepsin G and platelet activating factor, two neutrophil‐derived agonists
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Combined activation of platelets by cathepsin G and platelet activating factor, two neutrophil‐derived agonists
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机译：Combined activation of platelets by cathepsin G and platelet activating factor, two neutrophil‐derived agonists
Summary.In this paper we have studied the combined effects on platelet activation, of two polymorphonuclear neutrophil (PMN)‐derived agonists, namely platelet‐activating factor (PAF) and cathepsin G (Cat.G), used at threshold concentrations. Our results showed that the order of agonist addition was a determinant factor since the addition of Cat.G prior to PAF induced a full platelet activation while the reverse combination had no effects. The successive challenge of platelets by Cat.G and then PAF induced a strong aggregation accompanied by an enhancement of α and dense granule secretion. The observed phenomenon was also dependent on the time interval between agonist addition. It was significant at 30 s (P<0·05) and plateaued over 1–2 min. Platelet activation resulting from the combination Cat.G‐PAF can be described as a function of PAF concentrations, the synergism being significant between 10 Nmand 1 μm. The mechanism by which Cat.G primes platelets remains to be elucidated. However, some points have been examined and have led us to conclude that an increase in expression and/or affinity of PAF receptors, Ca2+imovements, protein kinaseCactivation and phospholipase A2pathway are not involved. Whatever the biochemical mechanism underlying this synergism which involved PMN and platelets, it may constitute a link between the inflammatory and haemostatic processes in response to tis
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