Characterization of liver regeneration stimulatory factor in human portal serum

Factors capable of stimulating DNA synthesis in rat hepatocytes (stimulating activity) were detected in the portal serum of patients after liver resection. The stimulatory factors were fractionated by gel filtration into four fractions with the molecular weights of 45,000-60,000 (fraction A), 1,500-2,500 (fraction B), 800-900 (fraction C), and about 700 (fraction D). Fraction A was inactivated by trypsin digestion or by being heated at 56 degrees C for 2 h, suggesting that this factor might be a protein. The stimulating activity in fractions B, C, and D was dose-dependent. These stimulatory factors seemed to be different from known hormones such as insulin and glucagon.