We reported a new placental protein having the anticoagulatnt activity in 1983.
This protein, placental coagulation inhibitor, later named Calphobindin (CPB), inhibited the coagulation cascade in which phospholipid and Ca++ ions are involved.
The inhibitory mechanisms of CPB on blood coagulation are studied, and the results obtained are as follows.
(1) CPB bound to phospholipid in the presence of Ca++ ions.
(2) CPB inhibited the factor X binding to phospholipid.
It is also possible that CPB interferes with another factors which bind to phospholipid, such as factor Xa and prothrombin.
These are the reasons why clotting system was inhibited by Calphobindin.
CPB concentrations in various fluid smples were measured by ELISA.
The concentrations of CPB in normal plasma {9.96±1.26ng/ml (n=15)}, pregnant woman's plasma {6.78±0.55ng/ml (n=15)}, pregnant women's urine {6.15±1.44ng/ml (n=14)}, normal ascites {128.65±14.54ng/ml (n=13)}, ascites in peritonitis carcinomatosa {599.23±185.07ng/ml (n=13)}, amniotic fluid {180.9±97.7ng/ml (n=43)}, and seminal fluid {4618.9±499.4ng/ml (n=9)} were shown in parentheses.
The reason why CPB concentrations are high in malignant ascites and seminal fluid is not clear.
CPB has 40% homology in structure with lipocortin and also exists phospholipase A2 inhibitor activity as in lipocortin.
Therefore, CPB may have complicated functions beside with anticoagulant activity.
