The overall and long term goals of the proposed research is an increased understanding of the mechanisms involved in fibrinogen biosynthesis. Particular emphasis and interest is directed at the understanding of those mechanisms and components involved in controlling the synthesis of plasma fibrinogen by parenchymal cells of the liver. Our recent studies indicate that rat fibrinogen fragment D90 (FDP-D90) (90,000 daltons) in micro molar concentrations directly and specifically induces the synthesis of fibrinogen by isolated hepatocytes in a chemically-defined, serum-free medium. Particular attention will be directed to identify and define the receptor on the hepatocyte responsible for the binding of FDP-D90. Additional studies will be performed to identify if this peptide is internalized and if the individual genes are stimulated to express increased quantities of mRNA for the Aalpha, B beta and gamma chains respectively by utilization of the appropriate genomic C-DNA probes. We will identify if cyclic nucleotides, cAMP, adenylate cyclase and Interleukin 1, protein kinase c, Ca++, and clamodulin are mediators of this synthetic path. Since it is possible that FDP-D90 may synergistically act with a """"""""cofactor,"""""""" detailed studies have been proposed to identify, isolate and purify this component and identify its cell of origin. Because we have recently demonstrated that human fibrinogen fragments D94 (94,000 daltons) and D78 (78,000 daltons) induce striking morphologic abnormalities in vascular endothelial cells, we propose continuation of these studies to identify the mechanisms involved. Expansion of the binding studies in progress will include verification of stimulation of cyclic AMP via adenylate cyclase. We will also measure secretion of prostacyclin and tissue plasminogen activator by Factor VIII:Ag and thrombomodulin to learn if these components that modulate thrombogenesis are disturbed by these fragments of fibrinogen. These comprehensive studies will provide new information on how rat fibrinogen FDP-D90 specifically induces the stimulation of the biosynthesis of fibrinogen and how human fibrinogen FDP-D78 and D94 induce damage in vascular endothelial cells.
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