Protein C: Rouen, a new hereditary protein C abnormality with low anticoagulant but normal amidolytic activities

A family is described in which venous thrombo-embolic disease is associated with reduced plasma protein C anticoagulant activity but normal levels of protein C amidolytic activity and antigen. The partial characterization of the heterozygous defect is described using crossed immunoelectrophoresis (CIE) with or without calcium and seven functional assays which differ by activators (thrombin-thrombomodulin complex, bovine thrombin and Protac snake venom) and by an eventual preliminary adsorption on insoluble salts. PC activity was thereafter determined either by chronometric or amidolytic assays. The results indicate that this abnormal protein C (PC) is normally activated and at least partially carboxylated. Three hypothesis are proposed to explain the discrepancy between normal amidolytic and low anticoagulant activities.