Thrombocytes

We offer the following platelet assays:

 

Acid Phosphatase

Quantification of platelets on a surface. Platelet enzymes can be quantified by specific substrates and further related to platelet count. This technique allows determination of platelet numbers on a biomaterial surface after blood incubation.

 

ATP

Platelet activation results in release of platelet products, stored in intracellular granules. These second-messenger molecules can induce recruitment and activation of platelets which are still free in solution. In this context, a sensitive and specific marker for platelet activation is the determination of platelet-released ATP. For the determination of ATP in plasma a sensitive test kit based on a bioluminescence reaction is used. This assay is applicable to ATP release by other cell types as well.

 

Beta-Thromboglobulin (BTG)

Beta-Thromboglobulin is a soluble protein stored in platelet granules. Agonist-induced platelet activation results in release of the contents of these granules, therefore plasma BTG levels are a marker for platelet activation. During blood collection, platelet activation might give rise to artifactually high BTG levels, therefore special collection tubes are recommended to prepare samples for this assay. BTG concentrations are determined via a chromogenic sandwich immunoassay.

 

Platelet aggregation

Platelet aggregation is an important physiological pathway in the process of hemostasis. Several agents are known to induce platelet aggregation, which can be studied in whole blood using impedance measurements or in platelet-rich plasma using turbidometric measurements. Exposure of platelets to ADP, arachidonic acid or thrombin induces platelet shape changes, release of several factors which recruit additional platelets and the assembly of surface-bound GpIIbIIIa complexes, which constitute receptors for fibrinogen. The generation of platelet-fibrinogen complexes ultimately results in the formation of large, irreversible aggregates. Exposure of platelets to collagen or ristocetin causes initial platelet agglutination, which is then followed by further platelet activation and irreversible aggregation.

 

Platelet Function Analysis (PFA)

Normal hemostatic processes depend to a large extent on platelet agglutination, activation and aggregation processes. Major defects in these processes can give rise to health problems related to bleeding. Platelet-plug formation tested under shear stress is performed in a shear-inducing device, which aspirates blood through cartridges coated with collagen/ADP or collagen/ epinephrine. Aspiration is achieved by a closed chamber which is kept at a diastolic pressure. This sensitive functional platelet assay reflects all haemostatic and thrombotic functions of platelets. The collagen/epinephrine test cartridge is the primary cartridge used to detect platelet dysfunction induced by intrinsic platelet defects, von Willebrand disease or exposure to platelet inhibiting agents. The collagen/ADP test cartridge is used to indicate if an abnormal result obtained with the collagen/epinephrine test cartridge may have been caused by the effect of aspirin or aspirin-containing medications.

 

Serotonin

Serotonin (5-hydroxytryptamine or 5HT) is an intermediate product of tryptophan metabolism, well established as a neurotransmitter in the central nervous system. It is primarily located in the enterochromaffin cells of the intestine, in serotonergic neurones of the brain and in blood platelets. Altered concentrations of circulating serotonin have been implicated in several pathological conditions including chronic tension headache, schizophrenia, hypertension, Huntington’s disease, Duchenne’s muscular dystrophy and early acute appendicitis. In the circulation more than 98% of serotonin is located in the platelets and is released during blood clotting. Serotonin in human plasma is determined with an immunoassay.

 

Thromboxane B2

Thromboxane B2 is a stable metabolite of thromboxane A2. Increased levels of plasma thromboxane B2 are an indicator for activation of blood platelets (Note: Thromboxane A2 is a potent activator of new platelets. It is involved in the recruitment of circulating platelets to form a platelet thrombus by means of irreversible secondary platelet aggregation). The antithrombotic effects of aspirin and asprin analogues is based on the inhibition of thromboxane release by irreversibly blocking cyclo-oxygenase, the thromboxane forming enzyme. Therefore, thromboxane release is a sensitive marker for platelet aggregation and for investigating the efficacy of cyclo-oxygenase inhibitors.