RESUMO
<p><b>BACKGROUND</b>The relationship between melanosis coli (MC) and aquaporin 8 (AQP8) has not yet been elucidated. The aim of this research was to investigate the relationship between the expression of AQP8 and the pathological mechanism of MC.</p><p><b>METHODS</b>Expression of AQP8 was detected by immunohistochemistry and reverse transcription-polymerase chain reaction (RT-PCR) in 37 MC colon tissues and 13 control colon tissues. Global gene expression analysis was also used to identify differently expressed genes. Its relationship with MC was analyzed by SPSS 11.5 statistical software.</p><p><b>RESULTS</b>The positive rate of AQP8 expression detected by immunohistochemistry in the MC group was 24.3% (9/37), significantly lower than the 69.2% (9/13) in the control group (P < 0.05). The relative expression level of AQP8 in MC group was 0.639 ± 0.160, lower than 0.921 ± 0.148 of controls (P < 0.05). Global gene expression analysis showed that AQP8 mRNA expression was downregulated in MC patients.</p><p><b>CONCLUSIONS</b>The decreased AQP8 expression in MC patients indicates that chronic use of laxatives containing anthraquinone may cause reduced water absorption. The expression of AQP8 may be related to MC.</p>