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SIN-1 partially and RGDS totally counteracts platelet aggregation as assessed in vitro by two independent whole blood
K E Karlberg1, J Chen, N Egberg
1Karolinska Institute, Department of Medicine, Huddinge University Hospital, Sweden.
Insights
Cyclic GMP stimulant SIN-1 and GP IIB/IIIA antagonist RGDS show different platelet antiaggregatory effects. RGDS acts as a total antagonist, while SIN-1 is a partial antagonist in whole blood aggregometry.
Area of Science:
- Pharmacology
- Hematology
- Biochemistry
Background:
- Platelet aggregation plays a crucial role in thrombosis.
- Understanding the mechanisms of antiplatelet agents is vital for cardiovascular disease management.
- Assessing antiplatelet efficacy requires reliable in vitro methods.
Purpose of the Study:
- To compare the antiplatelet effects of SIN-1 (cyclic GMP stimulant) and RGDS (GP IIB/IIIA antagonist).
- To evaluate these effects using two distinct in vitro methods: filtragometry and whole blood aggregometry.
- To determine the degree of antagonism (partial vs. total) for each agent.
Main Methods:
- In vitro assessment of platelet antiaggregatory effects.
- Utilized filtragometry to measure time to filter occlusion.
- Employed whole blood aggregometry with chemical stimulants.
- Measured dose-response relationships for SIN-1 and RGDS.
Main Results:
- Both SIN-1 and RGDS demonstrated dose-dependent antiplatelet activity in both methods.
- RGDS acted as a total antagonist, completely inhibiting platelet aggregation at higher doses.
- SIN-1 exhibited partial antagonism, with maximal effects being less potent than RGDS.
- Filtragometry indicated platelet activation across the filter, evidenced by increased beta-thromboglobulin.
Conclusions:
- RGDS is a potent, total antagonist of platelet aggregation.
- SIN-1 functions as a partial antagonist of platelet aggregation.
- Both filtragometry and whole blood aggregometry are suitable for assessing antiplatelet agents, revealing different mechanisms of action.
Abstract:
The cyclic GMP stimulant SIN-1 and the GP IIB/IIIA receptor antagonist RGDS were compared with regard to platelet antiaggregatory effects as measured in vitro by filtragometry and by whole blood aggregometry. In filtragometry platelet aggregation is measured as the time to partial occlusion of a filter in the test unit. Beta-thromboglobulin concentrations increased over the filter (p < 0.002) indicating that in filtragometry part of the mechanism of aggregation could be platelet activation across the filter. In whole blood aggregometry platelet aggregation is induced by a chemical stimulant. As tested in blood from healthy volunteers, linear dose-effect relations were found with both methods, for SIN-1 in the 10(-7)-10(-6) M range (p < 0.02, filtragometry and p < 0.05, whole blood aggregometry) and for RGDS in the 10(-5)-10(-4) M range (p < 0.0001, filtragometry and p < 0.02, whole blood aggregometry). At the highest dose RGDS totally counteracted platelet aggregation in both test systems. Maximal SIN-1 platelet antiaggregatory effects were less (p < 0.04, filtragometry and p < 0.01, whole blood aggregometry) than for RGDS. SIN-1 concentrations in the 10(-4) M range had no further antiaggregatory effects. In conclusion, with two principally different methods for the assessment of whole blood platelet aggregation, SIN-1 was found to be a partial antagonist while RGDS a total antagonist.