Effect of Ginsenoside Rb_1 on Rat Liver Phosphoproteins Induced by Carbon Tetrachloride

摘要

We investigated the effects of ginsenoside Rbt (G-Rbj), a major saponin from Panax ginseng C. A. Meyer, on rat liver protein phosphorylation after intraperitoneal administration of CCI4 alone or together with G-Rbt. We found that 118, 63, and 34kDa proteins were prominently phosphorylated in liver homogenates prepared from CG4-administered rats, while these protein-phosphorylations were inhibited in the homogenate prepared from the G-Rb! plus CCl4-administration group. When inhibitors of protein kinases were exogenously added to the homogenates from either the CCl4-administered group or the G-Rb! plus CCl4-administered group, their phosphorylations were inhibited much more by W-7, an inhibitor of Ca2+/calmodulin-dependent protein kinase (CaM-PK), than by H-7, an inhibitor of protein kinase C {C-kinase). Interestingly, only 34 kDa was phosphorylated in homogenates prepared from the corn oil-, G-Rbr, and G-Rbi plus CCl4-administered groups by the exogenous addition of sodium fluoride (NaF), an inhibitor of glycogen synthase. Additionally, G-Rbi inhibited the Ca2+-accumulation induced by CC14 both in liver homogenates and microsomes. The above results imply that G-Rb, inhibits the CCl4-induced protein phosphorylations by modulating CaM-PK rather than C-kinase, and that 34 kDa protein may play a different biological role in cellular environment from 118 and 63 kDa proteins. Therefore, a study in which G-Rbj is employed as a modulator of critical CCl4-induced phenomena ranging from the disturbance of Ca2+ concentration to protein phosphorylation may be successfully applicable to investigate the diverse physiological functions of liver.