In order to explore the role of prolactin (PRL) and the prolactin receptor (PRLR) during metamorphosis of amphibians, both cDNAs from the Chinese brown frog Rana chensinensis were identified. A PRL cDNA consisting of a 645-bp open reading frame and a PRLR cDNA consisting of a 1854-bp open reading frame were obtained. The amino acid sequence analysis indicated that there were 2 pairs of conserved Cys residues in both mature rcPRL and rcPRLR, and that their positions were conserved as well. Comparison of our results with those for other vertebrates implies that receptor recognition in anurans may not be pH-dependent. The relations of identity between rcPRL and other vertebrate PRLs resembled those of the identity between rcPRLR and other vertebrate PRLRs, suggesting that PRL may have coevolved with PRLR in R. Chensinensis. In addition, rcPRL and rcPRLR mRNA was detected via RT-PCR in various tissues of R. Chensinensis tadpoles. By using qRT-PCR, rcPRLR mRNA in the liver, skin, tail, and kidney tissue of different stages (stages 33-43) during metamorphosis was analyzed. The results showed that the expressional tendencies of rcPRLR increased throughout stages 33-43 in the four tissues, which was probably related to tissue remodeling.