Uptake of plasma fibrinogen into the alpha granules of human megakaryocytes and platelets.

P Harrison; B Wilbourn; N Debili; W Vainchenker; J Breton-Gorius; A S Lawrie; J M Masse; G F Savidge; E M Cramer

doi:10.1172/JCI114300

Uptake of plasma fibrinogen into the alpha granules of human megakaryocytes and platelets.

P Harrison, B Wilbourn, N Debili, W Vainchenker, J Breton-Gorius, A S Lawrie, J M Masse, G F Savidge, and E M Cramer

Published October 1, 1989 - More info

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Abstract

The origin of platelet alpha-granule fibrinogen (Fg), whether from endogeneous synthesis or exogeneous derivation, remains unknown. Although Fg biosynthesis by megakaryocytes (MK) has been suggested, recent studies have demonstrated that certain alpha-granular proteins originate primarily from plasma. To study the origin of alpha-granule Fg, platelet-associated Fg was measured by ELISA and Western blotting, and localized by immunofluorescence and immunoelectron microscopy in a patient with symptomatic congenital afibrinogenemia before and after replacement therapy with cryoprecipitate. alpha-Granule Fg was detected in the majority of platelets as early as 24 h postinfusion, suggesting that direct platelet uptake was occurring. Platelet Fg reached a maximum value of 42.5% of normal values at 3 d postinfusion and was localized in the alpha-granules, while plasma levels followed a typical half-life profile. Significant alpha-granule Fg was still detectable at 13 d postinfusion, with plasma Fg virtually absent. Studies on cultured CFU-MKs from the patient also confirmed that MKs can incorporate exogeneous Fg into alpha-granules. These results indicate that platelet alpha-granule Fg can be derived from the circulating plasma pool and that Fg uptake can occur in both platelets and MKs.

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Uptake of plasma fibrinogen into the alpha granules of human megakaryocytes and platelets.

P Harrison, B Wilbourn, N Debili, W Vainchenker, J Breton-Gorius, A S Lawrie, J M Masse, G F Savidge, and E M Cramer

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Uptake of plasma fibrinogen into the alpha granules of human megakaryocytes and platelets.

P Harrison, B Wilbourn, N Debili, W Vainchenker, J Breton-Gorius, A S Lawrie, J M Masse, G F Savidge, and E M Cramer

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