Figure 5.

The role of PGE₂/EP₄ in AVP upregulation of AQP2 expression in the CD cells. Primary rat IMCD cells were pretreated with an EP₄ antagonist ONOant and then treated for 24 hours with 10 nM AVP. AQP2 protein expression was determined by immunoblotting and normalized by β-actin. The medium was subjected to ELISA analysis of PGE₂. In a separate experiment, the cells were pretreated with PRO20 or anti–PRR-N antibody and then treated for 24 hours with an EP₄ agonist CAY. AQP2 expression was determined by immunoblotting. (A) Medium PGE₂ after treatment with vehicle or AVP (n=9 per group). (B) Effect of AVP with or without ONOant on AQP2 expression. (C) Effect of CAY with or without PRO20 on AQP2 expression. (D) Effect of CAY with or without anti–PRR-N antibody on AQP2 expression. The representative blots in B–D were from two or three independent experiments. Densitometry analysis was only performed on the representative blots (n=3 per group). Data are means±SEMs. CTR, control. *P<0.05 versus control; ^#P<0.05 versus AVP or CAY alone.