Red cell stroma, a stable standard for assessment of platelet procoagulant release

Platelet function in vitro may be investigated in various ways. One of the accepted methods involves examination of platelet procoagulant release. Optimal conditions relating to maximal release have not been defined. Red cell stroma phospholipid can substitute for the platelet procoagulant in many in vitro tests (Quick et al., 1954, 1957; Margolis, 1961; Lovric & Margolis, 1964). Using a multiple channel coagulation meter, an assay system was developed for testing both red cell stroma and platelet procoagulants. Maximum procoagulant release was obtained by lysing in alkaline hypotonic solutions or by sonication. The system was tested in a one-stage kaolin-activated platelet-free plasma substrate, obtained from fresh pooled citrated plasma. With this method the amount of available procoagulant could be related to the numbers of red blood cells or platelets. The results indicated that one platelet provided procoagulant equivalent to that derived from 0.7 red cells. Procoagulant release was studied under various conditions and expressed in terms of stable (red cell) standard. Platelets subjected to hypotonic stress or factor 3 release (Hardisty test) were studied quantitatively. The addition of sulphinpyrazone (Anturan) had no observable effect on platelet release in this system.