Platelet factor 3: Quantitation and characterization

Abstract

Platelet factor 3, isolated according to the method of Alkjaersig et al. (1), was heterogenous on 4% SDS-polyacrylamide gels. Procoagulant activity was lost after five days at 4°C. Optimal stability was at pH 7.2–8.3. The product contained 38% protein, 49% lipid and 8% carbohydrate. Activity was destroyed by phospholipases A, C and D, and trypsin. Delipidation of platelet factor 3 with sec-butyl alcohol or ethanol resulted in loss of all procoagulant activity. Recombination of the protein residue with the lipid extract restored 80% of the procoagulant activity if sec-butyl alcohol was used and 44% using absolute ethanol. Platelet factor 3 activated human prothrombin complex more rapidly than crude cephalin, which was inactive in the platelet factor 3 assay. Attempts to purify the protein components and maintain procoagulant activity have been limited by instability in deoxycholate, SDS and Triton.