Abstract
The hepatic stimulator substance (HSS) was prepared from weanling rat livers byultracentrifugation and Sephadex G-75 chromatography. The stimulatory effects of HSS oncell proliferation, EGF receptor expression and receptor tyrosine phosphorylation wereinvestigated in serum-free cultured human hepatoma cell line SMMC-7721. The resultsshowed: (1) The relative percentage of S-phase cells was increased in HSS-treated cells.(2) EGF receptor protein level was increased after the cells were beated with HSS for 12~24 h and this effect was dose- and time-dependent. (3) Treatment of the cells withHSS for 0. 5 ~ 15 min resulted in the autophosphorylation of EGF receptor tyrosine residuedramatically. The above results suggest that the proliferative action of HSS on hepatocytesfright be due to its modulation of EGF receptor expression and the signaling pathway.