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Aggregation of platelets with ADP
Medical expert of the article
Last reviewed: 23.04.2024
The processes of platelet aggregation are studied using an aggregometer that reflects the course of aggregation graphically in the form of a curve; ADP is used as an aggregation stimulator.
Before the addition of a proagregant (ADP), random oscillations of the optical density curve are possible. After the addition of the aggregate, oscillations appear on the curve due to a change in the form of the platelets. Oscillations decrease in amplitude, optical density decreases. Platelets combine into aggregates and the curve deviates upward (primary wave). When the ascent passes into the "plateau", a release reaction occurs, and the curve rises even more (secondary wave).
Under the influence of small doses of ADP on the aggregate, a double aggregation wave is recorded. The first phase (primary wave) depends on the added exogenous ADP, and the second phase (the secondary aggregation wave) is due to the release reaction of the intrinsic agonists contained in the granules of the platelets. Excessively introduced large doses of ADP (usually 1 × 10 -5 moles) lead to the fusion of the first and second aggregation waves. To achieve a two-wave aggregation, ADP is usually used at a concentration of 1 × 10 -7 moles.
When analyzing aggregation patterns, attention is drawn to the general nature of aggregation (one-wave, two-wave, complete, incomplete, reversible, irreversible), the difference between the optical density of the plasma before the beginning of aggregation and after achieving maximum aggregation (characterizes the intensity of aggregation), as well as a decrease in the optical density of the plasma for the first minute of aggregation or the slope of the curve in the stage of rapid aggregation (characterizes the rate of aggregation). It is important to note that the appearance of two-wave aggregation with stimulation of ADP and adrenaline in concentrations that cause a normally reversible aggregation (usually 1-5 μmol) indicates an increase in the sensitivity of platelets to these inducers, and the development of single-wave incomplete (and often reversible) at concentrations of 10 μmol and more - on the violation of the release of platelets. In clinical studies, the use of ADP at concentrations of 1 × 10 -5 moles (to achieve single-wave aggregation) and 1 × 10 -7 moles (for achieving two-wave aggregation) is generally accepted .
Aggregations for Weiss for ADP
|
ADP, μmol |
Aggregations are normal,% |
|
10 5 2 1 |
77.7 66.1 47.5 30.7 |
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