Adrenaline and noradrenaline upregulate platelets for fibrinogen binding

Abstract

Background: Acute coagulopathy is a common clinical complication after trauma, and contributes to posttraumatic multiple organ failure. The phenomenon may be due to the effect of stress hormones on platelet adhesion molecule expression after trauma. Catecholamine levels correlate with injury severity scores and changes of L-selectin expression on leucocytes, whilst adrenaline (ADR) alone also activates platelets. This study thus investigates the effects of ADR and noradrenaline (NOR) on platelets, at doses similar to those found in the plasma of normal and trauma subjects. Methods: Blood was taken from 19 healthy subjects and placed in tubes containing sodium citrate. Anti-platelet bound fibrinogen monoclonal antibody was used to identify the activated platelets while antiCD41 was used to identify platelets with and without activation. Five increasing concentrations of ADR and NOR (1, 3, 5, 10, 30 nmole/L) as well as one negative control (0.9% normal saline) and one positive control (10 µmole/L adenosine diphosphate/ADP) were prepared for the stimulation. A whole blood protocol was used in order to minimize any activation artefacts which might be created by centrifugation. Results: The percentage of platelets expressing fibrinogen receptors increased significantly with ADR and NOR even at the lowest dose (1 nmole/L) and continued to increase in a dose-dependent manner. Although the effect of ADR was greater than NOR in stimulating platelets to express fibrinogen receptor, the average number of fibrinogen receptors on each platelet was constant. Conclusion: ADR and NOR activated platelets to express fibrinogen receptors at doses that are similar to those found in the plasma of trauma patients.