Hepatocytes express blood coagulation factor XII (Hageman factor)

Area of Science:

• Biochemistry
• Cell Biology
• Hematology

Background:

• The liver is known to synthesize blood coagulation factor XII (Hageman factor).
• The precise cell type responsible for factor XII expression within the liver remained unidentified prior to this study.

Purpose of the Study:

• To identify the specific cell type responsible for factor XII synthesis in the liver.
• To investigate the transcription, de novo synthesis, and secretion of factor XII by primary rat hepatocytes.

Main Methods:

• Primary rat hepatocytes were cultured in serum-free medium.
• RNA blot hybridization was performed using a 32P-labeled human factor XII complementary DNA probe.
• Factor XII synthesis and secretion were assessed using radiolabeled leucine and cycloheximide inhibition.
• Western immunoblotting was used to compare secreted factor XII with authentic plasma factor XII.

Main Results:

• Hepatocyte cultures showed a 2.4 kilobase messenger RNA transcript for factor XII.
• Hepatocytes secreted de novo synthesized, radiolabeled factor XII.
• Immunoreactive and clotting activity of factor XII increased in hepatocyte cultures over 24 hours.
• Cycloheximide treatment inhibited factor XII accumulation.
• Secreted factor XII from hepatocytes matched authentic rat plasma factor XII in molecular weight.

Conclusions:

• Primary rat hepatocytes are confirmed to transcribe, synthesize, and secrete authentic factor XII.
• This study identifies hepatocytes as the specific cell type responsible for factor XII production in the liver.
• These findings contribute to understanding the hepatic regulation of the coagulation cascade.