Thromboplastin: Nomenclature and Preparation of Protein-Free Material Different From Platelet Factor 3 or Lipid Activator

Abstract

A method was developed for obtaining a highly active fraction from rabbit brain tissue which meets all of the requirements of a complete thromboplastin in the ‘traditional’ sense. The material we have isolated is called brain thromboplastin. This lipid fraction contains no protein. It is a complex consisting of sterol, glutamic acid, serine, ethanolamine and probably sphingosine. These components are also found in lipid activator and in the lipid portion of purified platelet factor 3, the latter being a lipoprotein. It is lethal upon intravenous injection in suitable quantity, while purified platelet factor 3 and or lipid activator are not. When the brain thromboplastin is combined with Ac-globulin and calcium ions, purified prothrombin changes to biothrombin, but such a change to thrombin does not occur when purified platelet factor 3 or lipid activator replaces the brain thromboplastin. For complete transformation of prothrombin to thrombin, it is sufficient to have the following proportions given on a dry weight basis: prothrombin 500, brain thromboplastin 80, and Ac-globulin 1. Heating brain thromboplastin to 100°C for 30 minutes or refluxing it with ether for 90 minutes impairs only very little of its activity but refluxing with alcohol for 90 minutes destroys its activity. However, then the material can still function as a procoagulant. The word ‘thromboplastin’ apparently now is utilized in all kinds of ways so that the meaning is diluted extensively. We use the term more specifically. The terms lung thromboplastin, beef lung extract thromboplastin, brain extract thromboplastin and lipid activator are used in terms of carefully considered descriptions related to preparations. To fulfill the requirements for generic designations, the word procoagulant can refer to all those substances and conditions that further the coagulation of blood while anticoagulant is the opposite designation.