Abstract
A new method for platelet aggregometry of whole blood has been developed. The method—screen filtration rate (SFR)—was based on a simple phenomenon that platelet aggregates in blood samples reduced the flow of specimen through a sheet of microsieve (20 micron square opening). In contrast to Swank's screen filtration pressure method, we determined the natural flow rate of the blood sample which had been fixed with formaldehyde (0.5%) and diluted to hematocrit value 10%, thus making time study capable and reducing the influence of viscosity on the flow.
Using this method, ADP-induced platelet aggregation in citrated whole blood was studied. Immediately after collecting blood in Na citrate, the sensitivity of platelets to ADP was extremely low. The aggregability then increased by one hour and decreased thereafter. This finding indicates importance of the conditions of sampling and storage of blood specimen as seen in Born's turbidometry.
Chlorpromazine, a membrane stabilizer, exerted a unique effect on platelet aggregation in whole blood. It inhibited the platelet clumping in whole blood at low concentrations which were not sufficient to inhibit platelet aggregation in platelet-rich plasma. This phenomenon suggested interaction between platelets and red blood cells during platelet aggregation.
Thus platelet aggregaometry in whole blood might provide a new view to the study on mechanism of thrombus formation.
