Optimization of Multiplate® whole blood platelet aggregometry in the Beagle dog and Wistar rat for ex vivo drug toxicity testing

This study was performed to optimize and standardize the use of the Multiplate® whole blood impedance aggregometer in the Beagle dog and Wistar rat for use in a research laboratory environment. The anticoagulants citrate, heparin and hirudin were compared and platelet aggregation responses to ADP, collagen, arachidonic acid and Par-4 agonist were evaluated to determine their half maximal effective concentrations (EC50) in blood containing low concentrations of a drug solvent (0.1% DMSO). The results indicate that citrate anticoagulation is not suitable for Multiplate® whole blood aggregometry because of the presence of spontaneous aggregation. ADP and collagen were found to be appropriate agonists for both species, whereas in the Beagle dog Par-4 agonist failed to induce aggregation and arachidonic acid induced platelet aggregation showed a high interindividual variability. The agonists EC50 calculated in hirudin blood were 2.70 μM ADP, 0.85 μg/ml collagen, 0.03 mM arachidonic acid and 165.7 μM Par-4 agonist in the Wistar rat, and 0.95 μM ADP and 0.23 μg/ml collagen in the Beagle dog.