Heparin

HEPARIN, a substance isolated by Howell and Holt from the liver, that prevents the clotting of blood. When obtained in a purified form, H. does not give protein reactions, gives a Molisch reaction (presence of a carbohydrate group), does not contain P and S; it is thermally stable—does not lose its properties when boiled. It is used in physiological experiments where it is important to prevent blood clotting. Recently, due to its harmlessness, it has been used in blood transfusions, as well as for experiments of "blood washing" in humans: blood released from the vessels, the clotting of which has been eliminated by H., is subjected to dialysis in collodion bags for the purpose of removing toxic metabolic products, and then is introduced into the bloodstream. H. began to be widely used in tissue culture work, especially if it is difficult to obtain unclo plasma from an animal of a given species due to the rapid clotting of its blood or for any other conditions. - Technique for obtaining "heparin plasma": 1 cubic cm of a previously autoclaved solution of heparin (1:1,000 physiological solution) is drawn into a syringe, and then 15-20 cubic cm of blood; the mixture is cooled and centrifuged. The resulting heparin plasma can be stored in sealed ampoules for many months. When in contact with a piece of tissue or a tissue extract, it clots quickly.