Increased number of thromboxane A2-prostaglandin H2 platelet receptors in active unstable angina and causative role of enhanced thrombin formation.

Abstract

The current study was designed to investigate the number and affinity of platelet thromboxane A2/prostaglandin H2 (TxA2/PGH2) receptors in patients with unstable angina and, if any, the role played by the increased thrombin formation that is a common finding in these patients. Measurements taken during active unstable angina but not those taken during inactive angina showed an increase number (p < 0.001), without changes in affinity, of platelet TxA2/PGH2 receptors, evaluated as the binding capacity of iodine 125-PTA-OH, a stable TxA2 analogue. Moreover patients with active angina had higher plasma concentrations of fibrinopeptide A (FPA) (p < 0.0001), which were significantly related to the number of platelet TxA2/PGH2 receptors (r = 0.76; p < 0.01). Heparin infusion but not aspirin treatment promptly normalized the number of TxA2/PGH2 receptors and significantly reduced plasma FPA concentrations. In an in-vitro study thrombin in a concentration similar to that found in vivo significantly increased the number of platelet TxA2/PGH2 receptors (p < 0.01), whereas heparin did not affect TxA2/PGH2 receptors. These results have important therapeutic implications and indicate the preferential use of heparin rather than aspirin during the acute phase of unstable angina.

• Authors: P A Modesti, A Colella, I Cecioni, A Costoli, D Biagini, A Migliorini, G G Neri Serneri
• Journal: American heart journal (Am Heart J) Vol. 129 Issue 5 Pg. 873-9 (May 1995) ISSN: 0002-8703 [Print] United States
• PMID: 7732975 (Publication Type: Comparative Study, Journal Article)

Chemical References

• Prostaglandins H
• Receptors, Prostaglandin
• Receptors, Thromboxane
• Receptors, Thromboxane A2, Prostaglandin H2
• Fibrinopeptide A
• Thromboxane A2
• Heparin
• Thrombin
• Aspirin

Topics

• Aged
• Angina Pectoris (blood)
• Angina, Unstable (blood, drug therapy, etiology)
• Aspirin (administration & dosage)
• Blood Platelets (chemistry, drug effects)
• Dose-Response Relationship, Drug
• Fibrinopeptide A (analysis, drug effects)
• Heparin (administration & dosage)
• Humans
• Middle Aged
• Physical Exertion
• Platelet Activation
• Prostaglandins H (blood)
• Radioligand Assay
• Receptors, Prostaglandin (analysis, drug effects)
• Receptors, Thromboxane (analysis, drug effects)
• Receptors, Thromboxane A2, Prostaglandin H2
• Thrombin (biosynthesis, pharmacology)
• Thromboxane A2 (blood)