Function of Heparin

BOTH heparin¹ and histamine² are now known to be concentrated in the tissue mast cells, and it might thus be expected that the release of histamine caused by damage to the mast cells would be accompanied by the release of heparin and a consequent increase in the clotting,time of blood. So far this dual effect has been observed in only one species, the dog, in which an intravenous injection of peptone or of a chemical histamine liberator such as compound 48/80 can release sufficient heparin to render the blood incoagulable. In the rat, however, although compound 48/80 releases histamine from the numerous mast cells in the subcutaneous connective tissue, the clotting time of the rat's blood remains unchanged. We have therefore attempted to discover what happens to the heparin in the rat following a maximal release of histamine by compound 48/80.