OBJECTIVETo investigate the cathartic effect of total anthraquinone (AQ) from rhubarb on SD rats and its regulatory effect on aquaporin 4 (AQP4) expression in rat colon and in vitro cultured LoVo cell line.

METHODSTwenty-four SD rats were randomly divided into the normal control group treated with distilled water, and the two AQ groups administered with AQ suspension in cathartic and high dose (AQcd and AQhd) respectively via gastrogavage for 5 days. Water content in colonic stool was detected and the expression of AQP4 in rat's proximal colon was measured using Western blot and RT-PCR. LoVo cells cultured in vitro were used in the experimental study. The AQP4 protein and mRNA expressions in the cells were detected by Western blot and semiquantitative RT-PCR after they were cultured for 24 h with RPMI-1640 medium containing rhein/emodin in different concentrations, and those cultured with RPMI-1640 containing 20 mg/L rhein/emodin for different time points.

RESULTSAfter treatment, the stool water content in the AQcd and AQhd groups was higher than that in the control group and the AQP4 expression in rats treated with AQ decreased in a dose-dependent manner. The study showed that rhein/emodin could significantly down-regulate the protein and mRNA expressions of AQP4 in cultured LoVo cells, with the effectiveness related with dose and acting time.

CONCLUSIONAt the same time of playing cathartic action, total AQ of rhubarb can effectively down-regulate the expression of AQP4 in rat's proximal colon; rhein/emodin can suppress the AQP4 expression in LoVo cells in vitro. One mechanism of cathartic effect of rhubarb AQ is possibly its down-regulation on AQP4 expression.