Experimental hemostasis in normal dogs and dogs with congenital disorders of blood coagulation.

By T. HovIG, H. C. RowsELL, W. J. DODDS, L. J#{216}RGENSEN AND J. F. NIUSTARD I NVESTIGATIONS of hemostasis and thrombosis in the microcirculation of animals during the past century have provided considerable insight into the mechanisms 69, 15, 16,30,33,51 63,64,66 The vessel wall, platelets and blood coagulation are recognized to be important. Hughes3’ considered that the speed with which platelets accumulate at the point of vessel injury is faster than can be explained on the basis of the known action of blood coagulalion. He32 found that platelets adhere to mesenteric connective tissue, and Bounameaux’4 observed that platelets adhere to subendothelial structures of the aorta in vitro. Studies by Zucker and Borrelli67 and by Hovig26’27 showed that platelets adhere to collagen and that this induces platelet aggregation. Hellem24 and Gaarder and associates1#{176} had already found that adenosine diphosphate ( ADP) from the red blood cells was able to cause platelet aggregation. Hovig28 and, subsequently, Spaet and Zucker6#{176} demonstrated that collagen induced platelet aggregation through release of platelet ADP. It is also possible that ADP may be released from injured cells in the vessel wall.’3 These observations provide a reasonable explanation for the mechanism by which platelets rapidly accumulate at a point of vascular injury. The part played by coagulation may not be important in these early stages, but the well-known fact that subjects or animals with coagulation disorders ( i.e., classic hemophilia ) have abnormal hemostasis clearly indicates that coagulation is necessary for establishing an impermeable, stable, hemostatic plug.”.’5’30’3656’6#{176} However, this is a complicated problem since subjects with one type of coagulation defect can have a more severe hemorrhagic disorder than those with another. In general, it appears that subjects with defects in the later stages of the intrinsic pathway of coagulation show a greater hemo-