GLYCOPROTEIN-IB BIOASSAYS - ACTIVITY LEVELS IN BERNARD-SOULIER SYNDROME AND IN STORED-BLOOD BANK PLATELETS

Glycoprotein lb (GP-lb) is a major platelet receptor protein concerned with von Willebrand-factor binding, platelet agglutination, and platelet adhesion, and it is required for normal hemostasis. By the use of botrocetin (venom coagglutinin), both quantitative and semiquantitative assays for GP-lb activity were developed. The latter assay uses limiting dilutions of botrocetin as a measure of GP-lb activity. Platelets, stored up to 23 days under blood bank conditions, were assayed by the limiting dilution test. Values of GP-lb were progressively diminished after 9 to 10 days of storage, reaching levels of less than 10% at 23 days. Platelets from a subject with Bernard-Soulier syndrome showed less than 10% GP-lb activity. These assays appear to be a specific measure of functional GP-lb activity, and, when combined with GP-lb antigen measurement by other methods, they provide a means for further characterizing GP-lb abnormalities.