β-Thromboglobulin ( βTG ) is a well known platelet specific a-granular protein, but
synthesis of βTG by human megakaryocytes has not been fully proved. A human megakaryoblastic
cell line ( MEG-01 ) was investigated for the presence of βJG in the culture medium
and cell lysates using a specific radioimmunoassay ( RIA ). The concentration of βTG
increased with time in the serum-free culture medium as well as in the cell lysates
as shown in the following table.
By an indirect immunofluorescent technique using a monospesific rabbit anti serum
against human βTG, βTG antigen was detected in MEG-01 cells. Immunoblot analysis of
culture medium revealed a single band ( mol wt 8,900 ) that is identical to the band
of human plasma βTG. De novo synthesis of βTG was demonstrated by the presence of
specific immunoprecipitable radioactivity in the medium after 5 h of labeling of the
cells with [35S]-methionine as a 8,900 mol wt protein. These results indicate that human megakaryocytes
produce βTG, The production of βTG by MEG-01 cells may be useful for the study of
megakaryocyte maturation and differentiation.
