Effect of blood platelets on heparin-induced clearing reaction

¹ Department of Medicine, University of Melbourne, Royal Melbourne Hospital, Victoria, Australia

The relationship between the fall in optical density and the rise in glycerol concentration which occur during heparin-induced clearing was studied in platelet-rich and in platelet-poor post-heparin plasmas. This relationship as determined by the significance of the regression coefficients was highly significant with both plasmas. The effect of platelets on clearing was studied in three system containing either fasting plasma or post-heparin plasma or a mixture of both plasmas. In each system platelets inhibited clearing as measured by fall in optical density but did not inhibit lipolysis as measured by production of glycerol. Addition of platelet-poor fasting plasma to platelet-poor post-heparin plasma inhibited lipolysis but did not inhibit clearing. It is concluded that there may be at least two inhibitors against clearing, one associated with platelets and one present in plasma, which inhibit optical clearing and lipolysis, respectively. When fasting plasmas were incubated with substrate endogenous clearing occurred frequently, but sometimes a rise in optical density and a decrease in glycerol concentration were found, suggesting reversal of enzymatic processes.