Radioimmunoassay of factor V in human plasma and platelets.
Homogeneous, single-chain human factor V was used to develop a double antibody competition radioimmunoassay to measure factor V concentrations in plasma and platelets. Standard curves were constructed that allow for the detection of as little as 20 ng factor V/ml of plasma. Normal factor V concentrations range from 4 to 14 micrograms/ml of plasma with an average value of 7.0 +/- 2.0 micrograms/ml (n = 64). No correlation was observed between antigen levels and age or sex. The radioimmunoassay data are consistent with factor V clotting assays, providing freshly drawn plasma is used in the bioassay. Radioimmunoassay of washed platelets indicate that 0.63-1.93 microgram of factor V is present per 2.5 X 10(8) platelets (4612-14128 molecules of the factor V platelet). When normalized to individual hematocrits and platelet count, the data indicated that platelets contribute approximately 18%-25% of the factor V found in whole blood. In addition, two individuals with functionally deficient factor V were examined and found to be deficient in both antigen and activity.
D000328:Adult; D000818:Animals; D001792:Blood Platelets / Q000032:analysis*; D005165:Factor V / Q000032:analysis* / Q000592:standards; D005166:Factor V Deficiency / Q000097:blood* / Q000276:immunology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010527:Perissodactyla; D010949:Plasma / Q000032:analysis*; D011863:Radioimmunoassay
D005165:Factor V