Clearance of Injected Heparin from the Blood

Abstract

HEPARIN is an extremely potent inhibitor of blood coagulation, and it is on the basis of this property that it has been widely accepted in the clinical treatment of thrombosis¹. It is a sulphur-containing mucopolysaccharide which is naturally present in a number of animal tissues, the highest concentration being found in liver and lung² and very minute amounts in the blood³. When heparin is injected into the bloodstream, its anticoagulant activity manifests itself immediately ; however, this effect is lost within a comparatively short period of time. The problem as to the fate of the administered heparin and its concentration in blood at different intervals after injection is therefore of considerable importance from a pharmacological and physiological point of view. Previous studies on the metabolism of heparin presented some difficulty, since the concentrations involved were minute and the possibility always existed of contamination by other sulphated mucopolysaccharides. The preparation in this laboratory of heparin labelled⁴ with sulphur-35 opened the possibility for tracing and quantitatively determining minute amounts of heparin in various tissues. The present communication is a report on the determination of heparin in blood subsequent to its administration as the labelled product. The correlation is shown between this concentration and the clotting time.