Effect of Contact Factor (Factor XII + Factor XI) on Aggregation of Platelets

Abstract

Inhibition of platelet aggregation by contact factor eluate (CFE) is demonstrated. A similar inhibition of platelet aggregation is found following incubation of ellagic acid with native platelet rich plasma. Inhibition of platelet aggregation by CFE or ellagic acid was not found when PRP from a patient with Hageman’ disease was used. The electrophoretic mobility of platelets was increased by the action of CFE. The possible role of the contact factor as a regulator of the platelet plug in the early stages of haemostasis is discussed.

Reduced Aggregability of Platelets in Rat Anaphylaxis

“…Aznar etal. [2] provided evidence that the in vitro activation of factor XII inhibits platelet aggregation. In our ex periments the in vivo administration of EA, a known activator of factor XII, exerted a similar inhibitory effect.…”

A New Family with Congenital Factor XII Deficiency

“…Patients with congenital deficiency of factor XII have little or no tendency to spontaneous haemorrhages [4] and, surprisingly, may have thromboembolic accidents [2] including thrombophlebitis, pulmonary embolism and particularly myocardial infarction [9]. No thromboembol ic attacks have been noted in members of this family.…”

Platelet Aggregation and Adhesiveness in Classical Factor X Deficiency and in the Abnormal Factor X (Factor X Friuli) Coagulation Disorder

“…Bang et al [2] have dealt with factor VIII, IX and XI defi cient plasmas and found that the 'activities' associated with these factors played no role in platelet aggregation. Several data have been presented indicating that factor XII either inhibits or stimulates platelet aggregation [1,2]. In a patient with Hageman trait a concomitant and distinct defec-…”