CsMRP4 mRNA was expressed at both developmental stages, in the metacercariae and in the adults, but the expression in the metacercariae was 1.91 times higher (Fig. 5a). This result suggested that the metacercariae might need the transcript for the efflux of bile acids from the fluke’s body during their survival in the bile duct of the final host. In the metacercarial stage of C. sinensis, diverse genes have been reported to be highly expressed in response to environmentally induced changes, such as sodium/bile acid cotransporter and several heat-shock proteins . Recently, the mRNA level of CsMRP7 was also reported to be elevated in the metacercariae .Fig. 5Differential expression of the CsMRP4 and reactivity of mouse anti-NBD1 immune serum. a Relative mRNA level of CsMRP4 gene in the adults and metacercariae of C. sinensis, measured using Q-rt.-PCR. b Reaction detected by western blot and immuno-ECL. The mouse immune serum reacted well with rCsMRP4-NBD1 (left) and specifically detected native CsMRP4 (right) in the crude extracts of C. sinensis. Lane NBD1: mouse anti-NBD1 immune serum; Lane Normal: normal mouse serum; Abbreviations: R, recombinant protein; N, native CsMRP4