We first confirmed the presence of estradiol receptors in the cytosol of rat hepatic sinusoidal endothelial cells and then studied the effects of Sho-saiko-to (TJ-9) on the level of these cytosol estradiol receptors. As a result, we found that estradiol receptors are present in the cytosol of hepatic sinusoidal endothelial cells from rats. Moreover, when these cells were incubated with TJ-9, the level of cytosol estradiol receptors increased. These results suggested that TJ-9 acts on hepatic sinusoidal endothelial cells to increase the level of estradiol receptors, thereby affecting the immune reactions in the liver.