Subunit B of factor XIII is present in bovine platelets.

Distribution of B subunit of coagulation factor XIII(FXIII B) in bovine platelets was determined. Intracellular location of FXIII B in platelets was confirmed by fluorescent antibody technique. Positive staining of FXIII B was observed with Triton-permeabilized platelets but not with non-permeabilized platelets. Immunoblots of plasma and platelet lysate revealed that the antibody was specific for FXIII B and this antigen existed in the supernatant of sonication-solubilized platelets. The amount of FXIII B in platelets was determined to be 17.3 +/- 6.7 ng/10(8) platelets by radioimmunoassay. This is the first visual and quantitative demonstration of intracellular FXIII B.