Heparin Counteracts the Antiaggregating Effect of Prostacyclin by Potentiating Platelet Aggregation

Summary

It has recently been reported that heparin neutralizes the inhibitory effect of prostacyclin (PGI₂) on human platelet aggregation. The mechanism of this interaction has not yet been unequivocally established. We present here evidence that heparin (Liquemin Roche) does not react directly with PGI₂ but counteracts its inhibitory effect by potentiating platelet aggregation. In the absence of heparin, PGI₂ was a less effective inhibitor of platelet aggregation induced by the combination of ADP and serotonin than by ADP alone. Moreover, the inhibitory effect of PGI₂ was similarly reduced when increasing the concentrations of ADP (in the absence of heparin). The lack of a specific interaction between heparin and PGI₂ is supported by the observation that, in the presence of heparin, other prostaglandins such as PGD₂ and PGE₁, and a non-prostanoid compound such as adenosine also appeared to lose their inhibitory potency. It is concluded that heparin opposes platelet aggregation inhibitory effect of PGI₂ by enhancement of platelet aggregation.

Keywords

Heparin - Prostacyclin - Platelet aggregation

• References

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