Fig. 3. Effect of apelin-13 on AQP2 mRNA expression. Upon reaching a transepithelial resistance of 4.5 kΩ.cm², mpkCCD cells were treated for 24 h with 10 nM dDAVP to induce endogenous AQP-2 expression (+ dDAVP) and then treated with 200 nM apelin13 for 8 h or 24 h in the continued presence of dDAVP. Left column represents the negative control (-dDAVP, -Apelin-13). RNA extraction and reverse transcription were performed as described in experimental procedures. Real-time qPCR was performed using specific primers for mouse AQP-2. Relative amounts of AQP2 mRNA were determined and normalized on the mGAPDH mRNA reported gene. Bars represent means ± SEM from five independent experiments, each performed in duplicate. §§: p <0.01; *: p <0.05.