A rat serum glycoprotein whose synthesis rate increases greatly during inflammation

Area of Science:

• Biochemistry
• Immunology
• Proteomics

Background:

• Inflammation triggers significant changes in serum protein concentrations.
• Identifying specific proteins involved in the acute-phase response is crucial for understanding inflammatory processes.

Purpose of the Study:

• To characterize a specific rat serum protein that dramatically increases during inflammation.
• To investigate the synthesis and concentration changes of this protein during acute-phase responses.

Main Methods:

• Crossed immunoelectrophoresis to detect changes in serum proteins.
• Protein purification using ammonium sulfate fractionation, DEAE-cellulose, Sephadex G-100, and concanavalin A-Sepharose chromatography.
• Molecular weight determination via equilibrium ultracentrifugation and SDS-PAGE.
• Measurement of [14C]leucine incorporation to assess protein synthesis.

Main Results:

• A specific alpha 1 globulin-like protein showed a substantial increase in concentration during turpentine-induced inflammation.
• The purified protein has a molecular weight of 56,000 Da, is a single polypeptide chain, contains 19% carbohydrate, and has an isoelectric pH of 4.7.
• Synthesis of this protein increased 20-fold during inflammation, while total serum protein synthesis increased only slightly.
• Serum concentration of this protein rose from 0.46 g/L to 7.2 g/L (10% of total serum protein) within 48 hours of inflammation induction.

Conclusions:

• This protein is a major acute-phase reactant in rat serum.
• Its synthesis is significantly upregulated during acute inflammation.
• The characterized protein's properties distinguish it from other known rat serum proteins.