The effects of emodin (EMD), sennosides (SEN) and Rheum polysaccharides (RPP) on the free calcium level in the isolated rat liver cells were studied with Ca2+ level 131.60 +/- 37.79 nmol/L in the liver cells. After adding CaCl2 (2 mmol/L) and KCl (120 mmol/L) to liver cell suspension sequentially, the free Ca2+ levels were significantly elevated compared with that of the resting status (P < 0.01). When the liver cells were pretreated with EMD (0.037 mmol/L) for 10 min, in the resting status or using the above doses of CaCl2 and KCl, the free Ca2+ levels were significantly increased compared with that of the control groups (P < 0.01). On the contrary, after administration of SEN (0.046-0.092 mmol/L) and RPP (0.1-0.2 mg/ml), the free Ca2+ levels were obviously decreased compared with that of the control groups (P < 0.01). Furthermore, the inhibitory effect was dose dependent. The opposite effects of the different active ingredients of rhubarb (EMD,SEN,RPP) on the free Ca2+ levels suggested that rhubarb has many kinds of regulatory function in the liver cells.