Partial characterization of a hepatocyte growth factor from rat platelets

Area of Science:

• Cell Biology
• Biochemistry
• Hepatology

Background:

• Rat serum exhibits potent stimulatory effects on DNA synthesis in primary rat hepatocytes.
• This stimulation surpasses that observed with serum from other mammalian species, including humans.

Purpose of the Study:

• To identify and characterize the factor in rat serum responsible for stimulating hepatocyte DNA synthesis.
• To compare the properties of this factor with known growth factors like human platelet-derived growth factor (PDGF).

Main Methods:

• Hepatocyte cultures were treated with rat serum, platelet-poor rat serum, and rat platelet lysate.
• DNA synthesis was measured by thymidine incorporation.
• The active principle was characterized by binding affinity, sensitivity to enzymatic digestion, gel filtration, and stability under various conditions.

Main Results:

• Rat serum stimulated thymidine incorporation, increased DNA content, nuclear labeling, and mitosis in hepatocytes.
• Normal rat serum (NRS) was twice as effective as platelet-poor rat serum (ppNRS).
• Rat platelet lysate (RPL) restored the activity of ppNRS, indicating a platelet origin for the primary stimulatory factor.

Conclusions:

• A hepatocyte growth factor derived from rat platelets accounts for 50% of the DNA synthesis-stimulatory activity in rat serum.
• This factor is a cationic polypeptide (approx. 65,000 MW), sensitive to heat, pH, and chemical treatments.
• While sharing some properties with PDGF, it appears to be a distinct molecular entity.