Synergism between collagen-adenosine diphosphate and collagen-epinephrine in platelets' aggregation: different dose response relationships.

OBJECTIVES: To evaluate the possible synergistic interaction of collagen-adenosine diphosphate and collagen-epinephrine in aggregation of human platelets. METHODS: An experimental study was carried out at Armed Forces Instiute of Pathology, Rawalpindi, Pakistan, from June 2001 to December 2002. The platelet aggregation was determined by means of turbidometric method, which measures changes in optical density of platelet suspension. After determining the sub-threshold values of each agonist with the help of dose-response curve, these agonists were added in pairs to determine the synergism between them. RESULTS: The differences between means of threshold and sub-threshold concentrations of agonists were significant (Collagen: P<0.001, ADP: P<0.001, Epinephrine: P<0.002). The responses of Collagen and Epinephrine in sub-threshold concentrations were synergistic in causing platelet aggregation, whereas there were no potentiating effects in response to that of Collagen and Adenosine diphosphate. CONCLUSION: The study reveals the synergistic potentiation of some of the agonists in circulation that might be responsible for the activated state of platelets and associated atherosclerotic complications.