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ADP-induced refractory state of platelets in vitro. I. Methodological studies on aggregation in platelet rich plasma
Abstract:
ADP-induced aggregation was determined at various times of incubation with ADP in unstirred human platelet rich plasma (PRP) to which adenosine deaminase was added. In the early stages of incubation the shape change response was absent, the aggregation response was poor, and not reversible. These three parameters returned slowly towards normal as the incubation proceeded. Pronounced impairment of the aggregation response was present after all added ADP had been degraded in plasma. Log dose-response (rate of aggregation) curves for the platelets incubated with ADP had shifted to higher ADP concentrations and had also a small decrease in maximal height and in the slope compared to those obtained with control platelets. However, the shift in log dose response to higher ADP concentrations was far more striking, so the increase in log dose (R) necessary to obtain the same rate of aggregation as with control PRP was taken as a measure of refractoriness of aggregation towards ADP. R increased with the time of incubation to an optimal value and then decreased. The magnitude of the optimal value and the time at which optimum was reached increased with the concentration of the ADP incubated with the platelets. The variations in R during incubation did not correlate with the breakdown of added ADP. The platelets began to recover their ability to aggregate with ADP while there was still ADP in the system.
Insights
Human platelets incubated with adenosine diphosphate (ADP) show impaired aggregation, with refractoriness increasing over time. Platelet function recovers even while ADP remains in the plasma, indicating complex recovery mechanisms.
Area of Science:
- Hematology
- Biochemistry
- Pharmacology
Background:
- Adenosine diphosphate (ADP) is a key mediator of platelet aggregation.
- Understanding platelet response to ADP is crucial for hemostasis and thrombosis research.
Purpose of the Study:
- To investigate the time-dependent changes in human platelet aggregation and shape change in response to ADP.
- To quantify platelet refractoriness to ADP during incubation and assess its relationship with ADP degradation.
Main Methods:
- Human platelet-rich plasma (PRP) was incubated with ADP and adenosine deaminase.
- Platelet aggregation, shape change, and log dose-response curves were measured at various time points.
- Platelet refractoriness (R) was calculated based on the shift in ADP concentration required for a specific aggregation rate.
Main Results:
- Early incubation stages showed absent shape change, poor, irreversible aggregation, and impaired responses even after ADP degradation.
- Log dose-response curves shifted to higher ADP concentrations, indicating increased refractoriness.
- Platelet refractoriness (R) varied with incubation time, peaking at an optimal value that depended on initial ADP concentration.
Conclusions:
- Platelet refractoriness to ADP is a dynamic process influenced by incubation time and ADP concentration.
- Platelet aggregation recovery can occur independently of complete ADP breakdown in the plasma.
- These findings highlight the complex interplay between ADP, platelet function, and recovery mechanisms.