The effects of human fetal hepatic stimulator substance (h-HSS) and liver cytosol (h-FLC) on the survival rate,the intensity of liver damage,and liver regeneration in rats with liver necrosis induced with D-galactosamine were observed.The physico-chemical properties of h-HSS were preliminarily determined.It was found that both h-HSS and H-FLC could markedly increase the.survival rate of the rats with toxic liver necrosis,significantly decrease the serum level of ornithine carbamoyl transferase and mitochondria aspartic trans-aminase,improve the hepaplastin activity,and elevate the incorporation rate of 3H-thymidine with liver DNA.h-HSS was stable after heated to 95℃ for 30 minutes,and sensitive to trypsin treatment.It demonstrated one major band at 15 000 daltons and 3 minor ones at 24 000,34 000,and 40 000 daltons respectively on sodium dodecyl sulfate-polyacrylamide gel electrophoresis.The relative content of the major band was 47.57%.

Ubiquitin-specific protease is a member of the deubiquitinating enzyme family,which can reverse the ubiquitination of proteins and stabilize proteins. It affects radiosensitivity of tumor by regulating DNA damage,cell cycle,nuclear factor-κB signaling pathway,Nrf2-Keap1 signaling pathway and oncogene c-myc. It is expected to become a new target for tumor radiotherapy sensitization.