Physical Factors in the Thromboplastic Activity of Phospholipids

Abstract

SummaryCephalin suspensions lose their thromboplastic activity when incubated with Tween or with sodium deoxycholate. This effect is proportional to the concentration of the surface-active substance, and to the length of its incubation with the phospholipids.The disappearance of the thromboplastic activity of cephalin treated with surface-tension lowering substances is due to the increased dispersion of the suspensions, as demonstrated by the decrease of their optical density. The activity of sodium deoxycholate is faster than that of Tween.The impaired thromboplastin formation in the presence of phospholipids treated with Tween or with sodium deoxycholate is not due to the formation of inhibitors.Cephalin incubated with surface-tension lowering substances and recovered by ultracentrifugation does not show any thromboplastic activity.Electron-microscopic studies show that incubation with surface-active substances causes the demolition of the structure of phospholipid-particle, on which the thromboplastic activity seems to depend.The size of the particles and the electric surface-charge seem to be among the main factors responsible for the thromboplastic activity of phospholipids.