Regulatory effect of anthraquinone derivatives from rhubarb on aquaporin 4 expression in colon of rats and in LoVo cell line / 中国中西医结合杂志

<p><b>OBJECTIVE</b>To 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.</p><p><b>METHODS</b>Twenty-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.</p><p><b>RESULTS</b>After 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.</p><p><b>CONCLUSION</b>At 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.</p>

Effect of total anthraquinone in rheum on aquaporin 2 expression in rat distal colon / 中国中药杂志

<p><b>OBJECTIVE</b>To investigate effect of total anthraquinone in rheum on aquaporin 2 expression in rat distal colon.</p><p><b>METHOD</b>SD rats were randomly divided into control group, low dose group, middle dose group and high dose group. Gavaged to control group, and treated group were administered saline and total anthraquinone in rheum with dosage of 0.14, 2.5, 4.5 g x kg(-1) x d(-1), respectively. All rats were put sacrificed after 5 days and stool in full length colon was gently collected to detect water content stool. Distal colon was removed to detect AQP2 expression with immunohistochemistry, western blot and RT-PCR.</p><p><b>RESULT</b>No diarrhea was found in low dose group and control group, there were not significant difference water content of stool and AQP2 expression between low dose group and control group. However, soft feces and loose stools occurred in diarrheic dose group, loose stools and watery stool appeared in high dose group. Stool water content increased in diarrheic dose group and High dose group, expression of AQP2 decreased evidently in these two groups (P < 0.01).</p><p><b>CONCLUSION</b>Total anthraquinone in rheum can reduce the transcription and translation of AQP2 in rats' distal colon, increase fecal water content, which probably is one of the mechanisms of diarrhea caused by total anthraquinone in rheum.</p>

Effect of rhubarb on expressions of aquaporin-2 and -4 in rat's kidney / 中国中西医结合杂志

<p><b>OBJECTIVE</b>To investigate the effect of rhubarb on expressions of aquaporin-2 and 4 (AQP2 and AQP4) in rat's kidney.</p><p><b>METHODS</b>Thirty-two SD rats were randomly divided into 4 groups, the normal control group, and the three rhubarb groups medicated via gastrogavage with low, mid and high dose of rhubarb extract (total anthraquinone) respectively. The 6 h and 24 h urine volume were measured, and the protein and mRNA expressions of AQP2 and AQP4 in renal tissue were determined with immunohistochemistry, Western blot and RT-PCR.</p><p><b>RESULTS</b>No significant difference between the control group and the low dose rhubarb treated group was found in urine volume, as well as in AQP2 and AQP4 protein and mRNA expressions. But the urine volume was obviously higher, the protein and mRNA expressions of AQP2 and AQP4 were markedly lower in rats after mid/high dose rhubarb medication respectively when compared with those in the normal controls (all P < 0.01).</p><p><b>CONCLUSION</b>Rhubarb can inhibit the protein and mRNA expressions of AQP2 and AQP4 in rats' kidney, which probably is one of the mechanisms of rhubarb for diuresis.</p>