EFFECT OF LOW CONCENTRATIONS OF PROSTACYCLIN ON PLATELET-FUNCTION IN-VITRO

The study was performed to determine the possible direct effects of lo w concentrations of prostacyclin that might spill over into the system ic circulation during the administration of inhaled aerosolized prosta cyclin. Platelet aggregation in response to adenosine diphosphate and collagen, as well as measurement of the maximum amplitude of the throm belastograph (TEG), was undertaken in vitro using venous blood exposed to low concentrations of prostacyclin (0, 10, 100 and 500 pg/ml) from eight healthy volunteers. There were statistically significant reduct ions in parameters of platelet aggregation in response to the agonists adenosine diphosphate (1 mu mol/l and 8 mu mol/l) and collagen (10 mu mol/l) following exposure to as little as 10 pg/ml of prostacyclin. T he maximum amplitude of the TEG was unchanged over the entire range of prostacyclin concentrations studied. The results indicate that low co ncentrations of prostacyclin or prostacyclin metabolite such as may be observed during inhaled aerosolized prostacyclin therapy are likely t o be associated with a marked platelet aggregation defect. This defect was not detected by the TEG.