Plasma pool source for fibrinogen synthesis in postabsorptive conscious dogs

Area of Science:

• * Physiology
• * Biochemistry
• * Nutritional Science

Background:

• * Hepatic protein synthesis is crucial for physiological functions.
• * Understanding amino acid sources (portal vein vs. hepatic artery) is key to hepatic metabolism.
• * Leucine and alpha-ketoisocaproate (KIC) are important amino acid metabolites.

Purpose of the Study:

• * To determine the relative contributions of portal vein- and hepatic artery-derived leucine and KIC to hepatic protein synthesis.
• * To investigate the role of precursor pool origin in fibrinogen synthesis.
• * To explore potential zonation in hepatic amino acid metabolism.

Main Methods:

• * Simultaneous infusion of dual-labeled leucine or KIC tracers in postabsorptive dogs.
• * Tracers administered via leg vein (systemic) and mesenteric (portal) catheters.
• * Measurement of tracer radioactivity in plasma and fibrinogen-bound leucine.

Main Results:

• * Fibrinogen synthesis predominantly utilized leucine delivered via the portal vein.
• * Hepatic artery contribution to leucine for fibrinogen synthesis was negligible.
• * Intraportal KIC showed limited direct contribution to fibrinogen synthesis.

Conclusions:

• * Hepatic fibrinogen synthesis relies almost exclusively on portal vein-supplied leucine.
• * Hepatic artery does not significantly contribute leucine for fibrinogen production.
• * Findings support the concept of zonation in hepatic amino acid metabolism and protein synthesis.